Sister Irmengardis Schatz pushed the few defiant strands of white hair back under her veil, sighed, took the convent library's letter opener, and reached for the stack of mail on her cluttered desk.
       Mother Superior had had her retire from teaching some twenty years ago when she turned sixty-five but then immediately given her full responsibility for running the convent's library.
       There weren't many users, but correct online cataloging of the more than two hundred thousand historical volumes, including incunabula, took up a great deal of her time.
       Her office was bright and cheerful, with light-pink walls, comfortable, tan furniture, well lighted for a room that was half underground. The shiny, white walls in the stack rooms were just as welcoming as the red and blue bookshelves.
       Sometimes, she missed teaching, arguing with and learning from students who were passionate about math and physics. Teachers she talked to at the conferences that Mother Superior still let her attend told her that students had changed, though, and that she was lucky to be retired from teaching.
       Maybe they were right. Her eighty-five-year-old body was neither as reliable nor as sturdy as it used to be. She needed new reading glasses almost every six months; her memory was more than faulty, and frankly, she couldn't concentrate as well as she used to.
       Naturally, there was value in preserving and protecting the convent's cultural heritage, but cataloging just wasn't as satisfying as teaching.
       Still, obedience was obedience, and that was one of the perpetual vows she had taken over sixty years ago. So, it was no question that she would do what Mother Superior told her to do. Nuns kept their promises and did what they could. Sometimes, setbacks turned into unexpected advantages.
       The Siessen convent itself had had its own ups and downs. The nuns were given land and buildings back in 1260. In 1634, during the Thirty Years' War, the Swedes came through and burned everything to the ground. The convent buildings weren't rebuilt until 1716.
       After the Napoleonic Wars in 1803, the Thurn and Taxis royalty in Bavaria grabbed the land and buildings and threw the nuns out. They got their convent back in 1860. In 1938, the Nazis threw them out and took over the convent grounds for the war effort. In 1946, the nuns returned once again.
       The convent's land and buildings, the size of a large college campus, were located on the treeless plains some three kilometers behind the sloping hills that almost hid the town of Bad Saulgau.
       The convent had been planned and built for at least two hundred nuns. When Sister Irmengardis entered the convent, there were forty postulants and thirty novices who took care of the building, garden, meals, and clothing so that the professed nuns could go about their work.
       Today there were just twenty aged or aging sisters and no hope for energetic young recruits.
       Still, there were limits. Not even a saint could catalog books for hours on end. Her bones and muscles complained more and more often about hours spent hunched in front of a computer. The sturdy, wooden cane next to her desk was there for a reason. When she wanted to stand up, she could never be sure that her legs would cooperate.
       Picking up the library's mail at the outside gatehouse was always a welcome diversion every morning as was lugging it back to her office in the basement of the main convent building. She liked to look down the hiking path from the gatehouse to Bad Saulgau.
       It wasn't all that long ago that she walked the three kilometers there and back every day while reciting her morning prayers. Now, the doctor said she always needed to take her cane with her when she risked walking long distances.
       There hadn't been much mail today. A small pile still lay on her desk. She reached for the oversized -- forty-five by thirty centimeters -- white envelope.
       The convent library didn't get much interesting mail; usually just misleading advertisements from the remaining media syndicates telling her what expensive combination packages of books and periodicals her library could subscribe to. Elsevier, Ciando, Schweitzer, and Springer were her most faithful pen pals.
       But this giant envelope couldn't be from those cutthroats. It was too sturdy and expensive, or at least the thick embossed paper gave her that impression. Just as she moved the letter opener toward the flap, the envelope opened itself, and a huge calendar flew out and floated above her desk.
       Sister Irmengardis stared and then stood up. Instinctively, she backed away at first, but the holograms of galaxies and stars that danced on the calendar pages made her want to stay. Just like they said in all the news reports. One glance at the calendar, and you were hooked, or at least many people were.
       She reached for the envelope. She hadn't noticed before; it was addressed to her personally and not to the library. The return address then, as expected, Parallel Times, with an address in Bad Saulgau.
       So, Bad Saulgau now had its own Parallel Times travel bureau. "That's interesting," Sister Irmengardis thought. The visiting space aliens were still unpredictable, along with all their other attributes. Sister Irmengardis, of course, found them fascinating.
       Bad Saulgau, a twelve-hundred-year-old town of about twenty thousand, was located in the Swabian Jura hills in Upper Swabia, north of Lake Constance, in Sigmaringen County. It was a nice little town, but nothing special, with the exception of an excellent hospital and several rehab clinics.
       Some tourists showed up occasionally, and people in the neighboring villages did their shopping there. Sister Irmengardis had no idea what attraction the town could have for the space aliens. They continued to set up travel bureaus in random locations all over the planet, and no one ever knew why they chose one place over another.
       The space aliens had shown up on the planet around five years ago, and everything about them was, well, still alien. No one could tell if they were some kind of hologram or if they were real creatures, just not entirely corporeal.
       The space aliens also all looked pretty much alike. They displayed a vaguely humanoid form, though shorter and slimmer than most human beings, and all seemed to wear some kind of light-gray coveralls and boots, again both made of an unknown material.
       They were definitely mega-multi-lingual. They communicated in a somewhat boring, accent-free manner in all the local languages without ever saying much or answering many questions.
       They didn't seem to eat or drink and were not at all aggressive. Earth inhabitants who tried to attack the aliens could never quite connect, and the aliens ignored them.
       Some people thought that they engaged in instantaneous teleportation. It was impossible to tell.
       When the space aliens first arrived, some of the even older sisters in the Siessen convent thought they were devils, but Sister Irmengardis was certain that was too simplistic a speculation. Why would devils go to so much trouble just to do basically nothing?
       After about a year, however, they did start to do something. Aliens showed up at the various supercolliders and talked to the researchers. In passing, they casually mentioned that there was an infinite number of parallel universes and that they themselves came from a neighboring universe.
       As evidence of their claims, they pointed out the various inexplicable particles and forces that resulted from supercollider experiments, naturally only existing for nanoseconds or even shorter periods of time. The aliens claimed that these particles and forces had more or less 'leaked in' from other universes.
       Many of their hints got research going in new directions. Then, the space aliens began to visit telescopes and telescope arrays, again not saying much, just dropping suggestions about what to look for.
       Every time there was a new discovery, it made all the news media, and Sister Irmengardis tried to learn everything she could.
       Back in what now almost seemed like another life, she had been an enthusiastic physics teacher, and she continued to try to keep up with developments in the field. To her credit, Mother Superior also continued to allow her to attend physics conventions.
       Then, the space aliens started advertising trips to parallel universes. They opened their Parallel Times -- time spent in parallel universes -- travel bureaus at what seemed to be random locations in large capital cities as well as in small towns or villages.
       The helpful staff at each travel bureau explained that they were offering trips to parallel universes, round trips if so desired, or extended one-way trips.
       Despite vague descriptions of what the trip might entail, thousands of potential travelers contacted the travel bureaus. Nonetheless, the aliens only chose about one out of a thousand applicants to take the trip.
       Some governments 'volunteered' the names of prisoners or dissidents for the trip, and occasionally, they were accepted, but only after affirming that they indeed wanted to go, or so the media reports claimed.
       Then, the space aliens started sending out calendars with astronomy holograms to attract new customers. Some people found the pictures compelling and begged to be allowed to go to the universes pictured in the calendars.
       For others, the calendars were just pretty pictures. Even when people begged to go, the space aliens again only selected about one in a thousand for a trip to another universe.
       Sister Irmengardis got the impression that all the travelers returned. At least many did. The aliens advertised that they were able to place people into specific locations in the space-time continuum of each universe and return them to where they left from.
       Those who returned didn't seem changed, but they only described their trips in vague terms, and all said that they needed time to understand the impressions they had experienced.
       And now, Sister Irmengardis had gotten an invitation. She couldn't think of a more unlikely candidate for inter-universe travel than an eighty-five-year-old nun with mobility and memory problems. And yet, she had always wanted to travel.
       An unfortunate bout with tuberculosis as a young nun had disqualified her from missionary work. She had accepted it as God's will but had never lost her desire for travel. She doubted that the space aliens would select her, but it would be interesting to see what this was really all about.
       Sister Irmengardis's first thought was to take her gift calendar and her cane for a walk to Bad Saulgau without informing Mother Superior. Mother Superior, at a youthful fifty, was the youngest of them all and generally a sensible person, but Sister Irmengardis didn't want to spend the time arguing with her.
       Mother Superior was a worrier who always wanted to mull things over for weeks or months before coming to a decision.
       It would be better and more efficient for Mother Superior to assume Sister Irmengardis was simply taking a foolish walk if she even noticed her absence. And yet, old habits were hard to break.
       Literally true. The nuns in Siessen had voted on whether they wanted to continue wearing their traditional habits or switch to civilian clothing with perhaps a small cross or short veil to make their vocations visible.
       The medieval clothing was difficult to justify anymore, and it was always a mistake to underestimate the potential for human stupidity. Some of the sisters had been harassed as ISIS terrorists in Bad Saulgau by Germans who couldn't tell the difference between a nun's habit and a hijab or burka.
       Sister Irmengardis continued to wear her long, black habit and veil. It just seemed like too much bother to give it up. The same was true of her vows. They no longer seemed so sensible or necessary, but she had promised to keep them and was in the habit of keeping her promises.
       So, she put the unresisting calendar back into the white envelope, locked her office, and went in search of Mother Superior.
       Mother Superior, formerly Sister Agatha Tiedemann, sat in her dark, little office and barely managed a brief half-smile when Sister Irmengardis knocked on her door and walked in.
       Mother Superior's narrow face was lined with deep wrinkles, the fate of many who maintained a minimal layer of subcutaneous fat. Sister Irmengardis's corpulent body mass guaranteed her a smooth, almost young-looking face, fat keeping her facial skin stretched out nicely. She found it only fair that there was one advantage to being overweight.
       Mother Superior tapped her bony fingers on the black metal desk, a nervous habit she never got rid of. She was always stressed, generally due to the financial situation of the convent.
       She never complained, but Sister Irmengardis, as one of the elder mentors in the convent, could always get her to vent. The convent had, in fact, long since stopped paying its own way.
       "What can I do for you, Irmengardis?" Mother Superior asked.
       "You look tired," Sister Irmengardis answered. It was always better to engage in some small talk before asking Mother Superior for anything.
       "I've been going over our finances again," Mother Superior said. "Things aren't improving." Sister Irmengardis thought she saw some desperation in the younger woman's eyes.
       "It will take some time before the convention business starts showing a profit," Sister Irmengardis said.
       At Sister Irmengardis's suggestion, Mother Superior had closed the boarding school after fewer and fewer parents were willing to buy their unmotivated daughters a college-entry, high school diploma. Many such daughters were now social media influencers who had no interest in higher education.
       Mother Superior had just begun to have the rooms remodeled and advertise the convent as a venue for religious-based conventions and theological education workshops. Sister Irmengardis herself had no idea how much money this new direction would bring in eventually, but they had to do something.
       "I know," Mother Superior sighed. "We have to be patient, but we're losing large sums and not taking in any money. At the moment, I don't know what else to do."
       "The convent could easily sell organic vegetables at the farmers' market in Bad Saulgau," Sister Irmengardis began. As a young postulant, Sister Irmengardis had enjoyed working in the gardens.
       "I know that the convent's gardens could produce much more than we need for the convent, but most of the sisters are too old to do serious farm work," Mother Superior said. "We certainly can't afford to hire help."
       "Maybe we could do something about the gift shop," Sister Irmengardis said.
       "We haven't made any money on the Hummel china figurines for decades, ever since the first company we licensed went bankrupt, just like all the others after that," Mother Superior said.
       "Copies of the drawings our Sister Maria Innocentia Hummel created are still the best-selling objects in the gift shop, but they barely pay for the shop's expenses."
       "Maybe we need to attract more guests," Sister Irmengardis said. "We have a beautiful campus area here. Everyone loves the St. Francis flower garden with its labyrinth. We need to do more to offer temporary stays in a convent for weeks or weekends. Other convents make a lot of money with that."
       "I don't know," Mother Superior said. "I'll have to give it more thought. But why are you here? You never come to my office without a reason."
       Sister Irmengardis pulled out a chair next to Mother Superior's cheap desk and sat down. "I got an invitation from the space aliens," she said as she handed the white envelope over the desk.
       Mother Superior looked up, startled. This was obviously not what she expected to hear. "I thought I'd take them up on their offer," Sister Irmengardis continued casually.
       "No," Mother Superior said firmly. "We can't do without you. And you can't risk your health or even your life like this. Don't even think about it."
       "I think I should gather more information first," Sister Irmengardis said blandly. "I have to confess, I haven't paid enough attention to the space aliens. Let me see what specific information I can dig up, and then we can talk again."
       Mother Superior glanced back at her computer. "Well, as our librarian and researcher, you, of course, are the information expert. See what you can learn, but right now, there is no way I would allow this risk." She handed back the envelope and calendar.
       Sister Irmengardis put the calendar back into the envelope, smiled, and left. She hadn't lied, and it wasn't her fault if Mother Superior assumed she would do her research online. Instead, she went back to her office and got her cane. It was summer, and she could count on several more hours of sunlight.
       The three kilometers to Bad Saulgau were mostly downhill, but she was still exhausted when she got to the travel bureau, fortunately located at the edge of town. She really needed to get more exercise, even if walking wasn't as practical as it used to be.
       The travel bureau was on the ground floor of a two-hundred-year-old stone building still in excellent shape, probably under monument protection. The aliens hadn't changed the building's appearance, just cleaned it up a little, especially the carved figures and gargoyles on the stone balconies.
       However, the front door looked suspiciously new. Sister Irmengardis wasn't sure what kind of metal the frame was made of. It was shiny and yet soft, letting her fingers sink into it.
       While she was trying to see how far her fingers would sink into the frame, the door opened, and a friendly voice called out: "Please come in."
       Sister Irmengardis walked inside the room. The floor and ceiling were a light gray, but the walls all contained the same holograms as the calendar, stars, supernovas, galaxies, and planets in motion.
       They should have made her feel dizzy -- those TV shows with all the rapid flashes of light certainly did -- but instead, she felt at home, at peace with herself, a feeling she truly hadn't experienced since she entered the convent all those years ago.
       One of the nondescript, short, gray aliens gestured toward a light blue, leather reclining chair in front of a dark gray desk, and Sister Irmengardis limped over to it gratefully. "Sister Irmengardis, or do you prefer Fräulein Schatz?" the alien began quietly in a pleasant though dull voice.
       Sister Irmengardis had to laugh. "I haven't heard Fräulein Schatz in a long time," she said. "My name is Sister Irmengardis. It's actually more than a name; it's my identity now. I'm a professed sister of the Third Order of Saint Francis here in the Siessen convent."
       The alien stared at some device on the desk for a few seconds, then blinked and looked back at Sister Irmengardis.
       "You received our invitation," it said. "Do you have any questions?"
       "Uh, you advertised a trip to a parallel universe," Sister Irmengardis began. "Just how safe is that? I mean, surely it's impossible for us fragile human beings to survive in a universe that could have completely different laws of physics."
       "We take care of that," the alien said. "And you have surely heard of creatures from your planet taking one of our trips and returning safely."
       "Yes," Sister Irmengardis said. "But they all have maddeningly little to say about their trips, other than that they now had a lot to think about."
       "Which shows that they returned in a safe, healthy, and mentally intact condition," the alien murmured.
       "But how do you do this?" Sister Irmengardis asked.
       "With all due respect to a creature well-versed in the physics of your time, I'm afraid that the explanations are a little beyond your understanding," the alien began.
       "You have learned that infinite numbers of universes exist, and you are correct; the composition, or rather the kinds of interactions among basic particles and forces, varies greatly from universe to universe. We have developed a kind of protective cloud that keeps our travelers in the conditions of their original universe while they travel among others."
       "What exactly do we get to see on these trips, and what are my chances of being selected to go?" Sister Irmengardis asked.
       "You have already been selected," the alien said, its voice not showing any emotion. "And we don't tell you what you might experience; we let you see for yourself."
       "How was I selected?" Sister Irmengardis asked. "And how did you guess that I would want to go?"
       "We don't disclose our selection criteria," the alien said. "However, as is the case for many sentient creatures, we are capable of telepathic communication. By the way, you will also have this capability during your trip so that you can zoom in on the thoughts of any creatures that interest you."
       "Well, what happens exactly? How and when do I go if I decide to take you up on your offer?"
       "You have already decided that you want to go," the alien said patiently. "You enter our transport chamber, where we engulf you in a cloud of the essence of your universe. At that point we present a selection of parallel universes telepathically that you might enjoy visiting."
       "Naturally, you can demand extended selection if none of the ones we present interest you. Then you think of the one you want, and off you go. As soon as you get tired of one universe, you send a telepathic request for suggestions and pick a new universe. When you're ready to come home, you just send out the respective thought."
       "And then I'm back here?" Sister Irmengardis asked. "But if I'm gone for a long time, what will I even find when I get back?"
       "You will return precisely ten minutes after you leave here," the alien said. "Inter-universe travel naturally involves time travel, as each universe possesses its own space-time continuum. Once you get back, we will copy your thoughts and impressions, and you can return to your previous life, or not, whichever you prefer."
       "That all sounds like magic," Sister Irmengardis protested.
       "You know about our previous travelers," the alien said. "Would you prefer to talk to them first?"
       "No," Sister Irmengardis said. "You know how badly I want to go. I just wish I knew why you want to send me."
       "Generally, our travelers understand more after they return from the trips," the alien said.
       "And that's your final word?" Sister Irmengardis asked.
       "When would you like to leave?" the alien asked.
       "I'm guessing you already know the answer," Sister Irmengardis said. "Where is this transport chamber?"
       She did have a funny feeling in her stomach when she entered the transport chamber at the back of the travel bureau. The gray door was almost invisible. It only opened after she touched the frame with her fingers. The metal was just as soft as the front door of the travel bureau.
       She walked in, but the chamber wouldn't let her cane accompany her. Some force pushed it away from the door. Once she was inside, the pictures began running through her mind, beginning with the holograms on the calendar but continuing with hundreds of others. If there was a protective cloud around her, she couldn't detect anything.
       She looked at the first picture, the one on the front page of the calendar and admitted to herself that she would like to go there. Then, she found herself in an interstellar space. Somehow, she could move from one blue giant star to another in an overheated universe. The stars were sentient and garrulous, more than willing to tell Sister Irmengardis everything about their environment.
       She thought about the calendar and wished for a broader selection. She couldn't decide about her next trip and so wished for one at random.
       Then she found herself on a planet that resembled Earth in many details, including a convent campus on a plain a little ways from a small city. The natives didn't resemble any life forms Sister Irmengardis knew; they looked and moved like two-meter-tall dust devils.
       But the convent campus seemed to be some kind of educational institution. In the different architectural partitions, groups of dust devils swirled and argued, sending their thoughts off, dancing in varying frequencies.
       The next universe Sister Irmengardis visited seemed empty and dark at first until she took notice of the virtual particles that zoomed in and out of existence. They were also sentient in their own way; it just took forever for bits of information to accumulate to form a message.
       The next universe was expanding so fast that Sister Irmengardis could barely keep up with the information flow. The universe after that had just exploded from its singularity. After a while, Sister Irmengardis quit keeping count of the number of universes she had visited. Since she was out of time, she also lost all sense of time.
       Then suddenly she wanted to go back. She felt a kind of responsibility, having had the opportunity to see and learn so much. More of the same, even if it was dissimilar in detail, no longer appealed to her. Every universe had been different, but she no longer wanted to experience the next different one.
       Back in the transport chamber of the travel bureau, she felt a kind of itch in her mind that then quickly went away. She opened the door, picked up her cane, and walked into the gray travel bureau. A different, short alien motioned for her to sit in a pale green recliner at his desk. "Do you have any questions?" it asked.
       "I don't know," she said. "I know now why you select life forms to travel the universes. You are gathering information and impressions. Every traveler sees and understands something different. The information accumulates and someone, probably you people, can use it to come up with hypotheses and theories. I still don't really understand why you do this other than out of curiosity."
       "What is the one thing all these universes have in common?" the alien asked.
       "Nothing that I can tell," Sister Irmengardis said.
       "All universes disintegrate eventually, one after another, one way or another. Now that we have managed to figure out how to keep our unique life forms functional for an unlimited amount of time, it is necessary to make sure that our universes don't just expand into a frozen nothingness. That would also kill us; we are a part of any universe we choose to reside in."
       "So, we need the help and insight of all possible intelligences in all possible universes. The more we know, the greater the chances we can keep universes in existence, up and running, you might say. Eventually, that will also help other life forms."
       "But why did you choose me; why did you choose the people you did from this planet?" Sister Irmengardis asked.
       "We have our algorithms," the space alien explained quietly. "We need people who are curious and persistent in their search for knowledge. We have no use for those who already think they know everything."
       "That even makes sense," Sister Irmengardis said. "And what should I do now?"
       "I think you'll figure that out," the alien said. "So far, everyone else has. Would you like us to transport you back to your convent? The walk down here wore you out. We can get you back there at the exact time you left."

       Sister Irmengardis stood at the gatehouse, leaned on her cane and walked back to Mother Superior's office. She needed to persuade Mother Superior to turn the convent into a specific think tank for cosmologists and physicists, a location where people could think about the fate of this universe and others.
       If done right, such a venue could earn the convent the money it needed, especially since she was certain she could hit up the aliens for support. That should persuade Mother Superior.
       Sister Irmengardis had to have a few good years left in her. She recognized, finally, that she had to start taking much better care of her health. She needed to get more exercise, both physical and mental.
       In the very long run, helping to find a way to keep universes in existence would be just as valuable as cataloging the rest of the library's incunabula. She just needed to take care of the remaining details.
       The convent could apply for the appropriate European Union grants to hire other librarians to finish the cataloging work. She had just never bothered to investigate this possibility before.
       Now, she was ready to do everything necessary to make the convent financially solvent and get her library cataloged. Then, the real work could begin.
       Time to get started. While this universe still had billions of years left, she didn't.