The sign said DO NOT ENTER UNAUTHORISED PERSONNEL ONLY which Alexi pointed out contained a grammatical ambiguity that was frankly their fault, not hers.

  "It could mean do not enter, unauthorised personnel only," she said, ducking under the yellow tape with the ease of someone who had been ducking under yellow tape since she was nineteen. "Which is an instruction directed specifically at unauthorised people. We have a permit. We are authorised. Ergo—"

  "Alexi."

  "I'm just saying the sign is poorly constructed."

  "Alexi, you've been justifying this for four minutes."

  "Good things take time."

  Tina followed her under the tape, adjusting the strap of her bag — canvas, overstuffed, with a broken zipper she'd been meaning to fix since March- and looked around at the site. It was an unremarkable patch of excavated earth on the outskirts of the city, surrounded by scaffolding and the particular silence of places that have been waiting a very long time for someone to pay attention to them.

  She loved it immediately.

  "Okay," she said. "What am I looking at."

  "Potentially a late Byzantine administrative complex," Alexi said, pulling out her field notebook. She already had three pens behind her ear. Tina had never once seen her use three pens simultaneously but the third pen was always there, a monument to preparedness. "Possibly earlier. The ground surveys flagged unusual subsurface density about six meters down, which could indicate- "

  "Alexi."

  "...a sealed chamber or series of chambers dating to-"

  "Alexi, normal words."

  Alexi looked at her with the expression of a woman who had accepted her fate. "There might be a room underground. A very old room. My professor thinks it's significant."

  "See? Was that so hard?"

  "I have a degree."

  "You have two degrees and somehow you still can't explain things without footnotes." Tina was already walking toward the main excavation trench, peering down into it with her hands on her knees. The earth was dark and layered, different centuries stacked on top of each other like geological lasagne. She found this unreasonably exciting. "So we're going down there?"

  "I'm going down there. You are here to observe and under no circumstances to touch anything."

  "Obviously."

  "Tina."

  "What?"

  "That obviously sounded extremely suspicious."

  Tina straightened up and looked at her with wide, innocent eyes. Alexi had known her for six years. She was entirely unmoved.

  "I just want to look," Tina said. "I'm a scientist. Looking is what I do."

  "You're a learning scientist. You study how people acquire knowledge. This is a fifteenth century Byzantine excavation site. These are not the same field."

  "Knowledge is everywhere, Alexi. That's literally the first thing they teach you."

  "That is absolutely not the first thing they teach you."

  "It should be."

  Alexi made a sound that had no English spelling and started down the ladder into the trench.

  The room was smaller than Tina anticipated and more beautiful than she had any reason to expect.

  They had arrived via a narrow passage that required Alexi to crawl through, while Tina, being the shorter of the two, moved through it with much more dignity a detail she only pointed out on two occasions. At the end of the passage, the chamber revealed itself as a roughly circular room with stone walls, its air cool and peculiar, as if it had not circulated for centuries.

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  Someone had etched markings into the walls. Not for decoration, with intention. Maps that Tina gradually understood, as she turned in the glow of Alexi's flashlight. The entire room was filled with maps. Coastlines, city shapes, and mountain ranges depicted with meticulous, detailed lines stretching from floor to ceiling, overlapping in some areas, with some clearly being older than others. A room where someone had spent a significant amount of time capturing the world around them.

  "Ah," Alexi said gently. It was the sound she made when something was important.

  "Right," Tina said in agreement.

  They stood in silence for a moment, which was unusual for them.

  In the centre of the chamber, resting on a low ledge that protruded from the wall like an altar, was a collection of items. A cracked ceramic vessel, a book that once was, now mostly just an idea. A piece of cloth folded and so aged that it had taken on the color of the surrounding stone.

  And a compass.

  Brass, small, surprisingly intact. Tina could make out from where she stood that the case had something engraved on it — a map, she thought, though the detail was too intricate to read at this distance.

  "Don't touch anything," Alexi said, moving toward the walls with her notebook open, already sketching.

  "Obviously," Tina said.

  She picked up the compass.

  It was warm.

  That was the first mistake- it should have been cold, absolutely cold, as if untouched by warmth for centuries, like the temperature of a room that hadn't felt sunlight since the collapse of an empire. But it rested in her hand as if it had just been held, as if it had been waiting at exactly body temperature for this very moment.

  The engraving on the case was a map. She tilted it toward the light. The coastlines were recognizable and yet not, like a variation of a place she knew, something she dreamed sideways. At the center of the map, where north would typically be indicated on a regular compass, there was a small symbol she couldn't decipher and an arrow that wasn't pointing north.

  It was pointing at her.

  She looked up. She meant to say Alexi, come look at this. She genuinely meant to say that.

  What happened instead was the floor.

  Specifically: the floor stopped.

  Not collapsing - nothing so dramatic. It simply ceased to be the kind of floor you could stand on, the way a word stops meaning anything if you say it too many times, and Tina had approximately one second of oh no before the chamber, the maps, the centuries-cold air, all of it, folded around the compass in her hand and took her with it.

  She heard Alexi shout her name.

  Then she heard nothing.

  The archive smelled like beeswax and old paper and something floral she couldn't identify.

  Tina lay on a stone floor a different kind of stone, warmer to the touch, with the smooth texture that comes from being stepped on by countless people over many years and gazed up at a ceiling adorned with painted beams, clearly and calmly thinking to herself: I have made a mistake.

  The compass was still in her hand.

  She sat up. She was in a large room lined with shelves, the shelves lined with manuscripts and scrolls and bound documents, the light coming from narrow high windows and from oil lamps in iron brackets on the walls. A wooden table ran down the centre of the room, covered in open books and inkwells and the general administrative evidence of people who had been here recently and would be back shortly.

  An archive.

  She had landed in an archive.

  Some deeply inconvenient part of her brain noted that the manuscripts on the nearest shelf were extraordinary, the script Byzantine Greek, the illuminations visible from here, the condition remarkable, and she absolutely should not be thinking about that right now—

  Footsteps.

  Tina shoved the compass into her bag, stood up, and arranged her face into an expression she hoped communicated I am supposed to be here rather than I have just fallen through time and I cannot actually remember what century this is.

  A monk appeared in the doorway.

  He was elderly, slight, with the careful eyes of a man who had spent decades reading things people tried to hide. He looked at Tina — her canvas bag, her very modern clothing, her hair, her shoes — with a slow, methodical attention that made her feel like a manuscript being catalogued.

  He said something in Byzantine Greek.

  Tina's Byzantine Greek was, charitably, nonexistent.

  She smiled. It was a very good smile, professionally speaking — she used it in research presentations when a question had exceeded her expertise. It conveyed I am competent and trustworthy while meaning please give me thirty seconds.

  The monk waited.

  "I'm a scholar," Tina said, in careful modern Greek, which was to Byzantine Greek roughly what a bicycle was to a war galley. "From f-far away. I study..I study learning- And history-" She paused. "I got a little lost."

  The monk looked at her bag. At her shoes. At the spot on the floor where she had, until very recently, not existed.

  He said something else, slower this time, with the patient enunciation of a man who had taught novices for forty years.

  She caught maybe one word in five.

  "Yes," she said, because it felt like the right answer.

  He seemed to accept this. He gestured at the table- sit- and disappeared back through the doorway, his footsteps receding into the building.

  Tina sat. She put her bag on her lap. She breathed.

  She looked at the extraordinary manuscripts she was absolutely not thinking about.

  She thought: Is this a dream? Where am I? Where is Alexi? I-I was just now standing and now- God. Is this the caffeine? Am I dead? Is this the heavens? I- Okay. Okay. You are a researcher. This is just a different kind of fieldwork.

  The monk came back with tea, which Tina accepted with both hands and genuine gratitude, and began asking her questions she only partially understood, and outside the archive windows the city of Constantinople- gold and impossible and ancient and alive- went about its business entirely unaware that somewhere in its streets, a historian in fieldwork clothes was about to become a serious problem for a noble family, and somewhere in its palace, a prince who had forgotten his own name was copying someone else's records in a room with no windows.

  The compass needle hadn't stopped moving.

  It was looking for him.