The ache in Tess’s shoulders moved to her head. She wished the Morningstarrs had simply drawn a treasure map like normal people. But then, if they had done that, someone probably would have found it years and years and years ago, and grabbed the treasure for themselves. And Grandpa Ben might have never grown up in 354 W. 73, and neither would her mother, and if her mother hadn’t lived there, would she have ever met her father? Would Tess and Theo have ever been born? Grandpa Ben once told her about something called the butterfly effect, where one tiny event could affect a million bigger things, like the flapping of the wings of a butterfly could influence the formation of a hurricane weeks later. If you started reimagining the past, you could change your own existence, or undo it completely, which was just too weird to contemplate.

Tess consulted the list of museums for the next one to call. “The 2nd City Reliquary,” she said aloud.

“2nd City?” said Theo. “Isn’t that what they call Chicago?”

“Reliquary,” Jaime said. “A place they keep relics. Like Ada said in the letter.”

Why would there be a museum dedicated to Chicago relics in Brooklyn? Tess dialed the number anyway.

A rumbly voice said, “2nd City Reliquary.”

“Hi. I’m doing a group project for school about puzzles and I was just wondering if—”

“School? Isn’t school out for the summer?”

“It’s a very special school. We go all year round.”

“Cool!” said the rumbly voice. “What are you looking for?”

“I’m looking for a certain kind of puzzle. It’s a cube made up of a bunch of smaller cubes, and you have to rotate them to—“

“Oh! Yes! We have one of those around here somewhere.”

“You do?”

“Yep!”

“Okay, then,” said Tess.

“Okay!” said the rumbly voice.

“One more question,” Tess said.

“Sure.”

“Why do they call your museum the ‘2nd City Reliquary’?”

“Because it’s the second one.”

“Was there a first one?”

“Sure!” said the rumbly voice. “Until one day it disappeared.”

“Uh . . . disappeared?”

“One day it was here, next day the whole thing was gone. And I don’t mean the shelves were cleared out, I mean the entire building was just . . . gone. Poof! As if it had never been built. Weird, huh?”

“Not as weird as you think.”

CHAPTER TEN

Theo

Brooklyn was only a half hour away, but it might as well have been another country. The streets around the place were packed with tattooed girls in denim shorts over tights, and boys who dressed like farmers from 1825. Beards were long and lush, mustaches wide and waxed.

A skinny brown guy in striped pants and roller skates twirled around Theo twice. “Dope ’fro,” he said, then skated off into the crowd.