“You know why,” Tess said. What Tess did not say, did not have to say, was that Slant was all over television and social media telling people how he would reshape New York City into the “city of the future”—whatever that meant. That he was talking about starting his own school so that he could “imbue the minds of the future with the values of the future”—whatever that meant. That he was backing political candidates and research groups that Tess’s dad claimed were “shady as all get-out”—whatever that meant. That Slant seemed to be more powerful than ever. That they had not managed to save their own home, but maybe they could save someone else’s. That the destruction of 354 W. 73rd Street had to mean something. And it wouldn’t mean anything if they didn’t solve the Cipher.

After a few moments, Jaime said, “We can’t let him win.”

They all knew who “he” was. They started to move, slowly, carefully, while Nine urged them along. With each step, tiny lights overhead sputtered to life, casting a dim green pall over everything, as much good as that did. Nothing to see but endless walls of stone. They seemed to be in some sort of tunnel running underneath the building.

“Do you guys feel that? There’s a slight pitch in the floor,” said Theo. “This passageway is leading us down.”

“Awesome,” said Jaime. “I’m sure that’s nothing to worry about.”

Tess stayed quiet, even though the questions were itching to burst from her mouth. Leading them down where? What if the tunnel collapsed on their heads? What if it led them straight through the island and then out to sea? What if a battalion of Underway conductors or Rollers or Lances or moths were lying in wait for them?

What if they failed again?

Nine turned and gave Tess’s fingers a gentle nip. She always knew when Tess’s mind was churning. She was a Cat, after all. But despite Nine’s calming presence, Tess shivered. “It’s cold.”

“Yeah,” said Jaime. “And quiet. I don’t hear the Underway trains. Do you?”

“No,” said Theo. “Walls and floors must be too thick.”

Jaime touched the stone on the walls. “There’s something written here.” He ran his fingers over the faint markings. “A name. Sam.”

“No last name?” Tess asked.

“Just Sam.”

They kept walking, the pitch of the stone floor getting steeper. From time to time, Jaime stopped and read another name etched into the stones. Beulah. James. Sissy. Solomon. Patrick. More often, there were simple Xs scratched into the stone, as if someone had only wanted to leave a mark.

“So many,” Tess said. “But if the door we came through was the only entrance to this tunnel, and that door was hidden until now, how did anyone get into this tunnel?”

“Maybe the people who built it signed their names,” said Theo.