He waited until they were outside of the library before he said, “We have to come up with a better cover story for what we’re doing. We can’t just keep running around the city, telling everyone what we’re looking for.”

“But we’re not,” Tess said.

“We just told that librarian about the letters we wanted to see. We could have found them ourselves. What if the librarian mentions it to someone else or writes it down in some log or something? What if . . .” He paused, all sorts of horrible scenarios straight out of stories and movies racing around his skull. “What if somebody questions her? Or threatens her?”

Theo shook his head, but his eyes widened with alarm. “That’s why we hid the clue.”

“Someone else could find it. We’re not the only ones trying to figure out the Cipher.”

“Yes, but we never were,” said Tess.

Jaime jammed his hands in his pockets, trying to explain. “Ever since 354 West 73rd came down, I don’t know. It’s been different. I’ve felt different. And don’t tell me it’s because I live in Hoboken.”

“It’s because you live in Hoboken,” Theo said, almost automatically. Then he held up his hands in surrender. “No, I know what you mean. Things have been . . . strange.”

Tess swallowed hard, and Nine licked her fingers to soothe her. “That blond woman was the strange one,” she said. “Who do you think she is?”

“Probably nobody,” said Jaime. “But I don’t want to meet her again.”

“No more run-ins with icky strangers,” Tess said. “Agreed.” She reached behind her and tightened her braid with a quick tug. “Let’s get out of here. We need a break. Want to come back to Aunt Esther’s? We can grab something to eat.”

“Fig Newtons?” said Jaime.

“Theo makes a mean sandwich,” Tess said.

Theo said, “I make a good sandwich.”

Later, in the twins’ attic room, Nine sprawled like a rug on the rug. Remnants of a too-late lunch—plates and balled-up napkins and blobs of cheese hardened to adhesive—littered the floor all around them. Jaime liked this room, cozy and messy as it was. He peeled off a stamp of cheese from his plate and popped it in his mouth, reminded of something else Mima always told him: When you’re feeling nervous and out of sorts, eat something. You might just be hungry.

Mostly, it was true.

“Well,” Jaime said. “That sandwich was both good and mean.”

“Theo, himself, is both good and mean,” said Tess.

“Mean,” said Theo, “is usually a matter of perception.”

“You sound like a comic-book villain,” Jaime told him.

“Yeah, when they’re monologuing about how they and the hero are really a lot alike,” Tess said. “Two sides of the same coin.”

Theo pulled a Fig Newton off a platter. “About this clue.”