Leo fingered the scroll and said, “This isn’t paper or parchment. It’s papyrus. That might mean you were in Greece, or Rome, or Egypt.”

“Well,” said Kat brightly. “This place you saw. Can you describe it again?”

Isaac did, adding as many details as he could.

“I think I know where you might have been,” Kat said, “and maybe who she was. She’s one of my personal heroes. I’m thinking you were in the great Library of Alexandria.”

“The Library of Alexandria!” exclaimed Leo. “What I’d give to see that.”

“In fact,” Kat continued, “you might have been in the last bit of the Library, most of which was destroyed. And the woman, if I’m right, would have been Hypatia, because she was a famous mathematician who lived in Alexandria around AD 400.”

“Golly,” whispered Colin.

“Hypatia’s father was one of the last members of the library. She was far ahead of her time. The patriarch of Alexandria decided to exile the Jews who lived there and confiscate their property. Hypatia was friendly with the Roman prefect who supported the Jewish people, and that made her the patriarch’s enemy. So, it’s believed that he had her murdered. Some legends say she was murdered in broad daylight, on the street, by an angry mob.” She paused, and then said, “History repeats itself. I’m so sorry, Isaac.”

Isaac swallowed the lump in his throat. It felt like there was no place safe for people like him, not even in past history. And he grieved again the loss of Hypatia. Even though it sounded like he wasn’t responsible for her death, maybe if she’d been able to escape through that magical door rather than help him retrieve the watch . . .

“The astrolabe fits, too. Hypatia was known to have used them.”

“What’s an astrolabe?” Colin asked.

“It’s an astronomical orrery. It shows the positions of the stars and planets. Hypatia was brilliant, really,” Kat finished, and sighed.

“Did you see that?” Leo asked. He’d been studying the scroll. “Did you see what it just did?”

The others leaned over again.

“It moves,” Colin said. “The images move.”

“I saw that, too,” said Isaac. “It makes it hard to read the words because they are always changing.”

“Interesting,” Kat murmured.

“I can’t make it out,” Colin said.

“Well,” said Kat, “I think it’s time to make a list of what we know and what we don’t.” She went to the desk to fetch a paper and pencil. Amelie nudged Isaac and he met her eyes and then Leo’s and Colin’s and everyone smiled.

Kat’s orderly manner, Isaac realized, could be annoying, but in this moment of confusion it was also most welcome.

Kat sat down again and looked around at the others. “What?” she said.

“We’re just admiring how you think,” Amelie said sincerely.