“Do what?” Tess and Jaime said, and laughed. For one moment, it was as if the tragedy of 354 W. 73rd Street never happened, that they were the same as they used to be. Tess tried to hold on to the feeling.

After they finished their breakfast and helped wash the dishes, they went upstairs. Jaime pulled out his sketchbook and wrote the word COUNTESS across the top of the page.

“HA! Told you it was an awesome joke,” Theo said.

“If this actually is the key word, it’s no joke,” Jaime said.

They consulted the Vigenère table they had found the day before:

FCHBMFWSHFUVWSXLJSMCBHWJU

“So,” Jaime said. “The key word countess gives us the order of the different alphabets. First, the C alphabet; next, the O alphabet; after that, the U alphabet.” He wrote the key word three times plus one extra C. Underneath that, he wrote the ciphertext:

COUNTESSCOUNTESSCOUNTESSC

FCHBMFWSHFUVWSXLJSMCBHWJU

On the chart, Tess went to the C alphabet. “In the C alphabet, the letter F represents the plaintext letter D,” she said.

Jaime wrote D underneath the ciphertext.

COUNTESSCOUNTESSCOUNTESSC

FCHBMFWSHFUVWSXLJSMCBHWJU

D

“In the O alphabet, the cipher character C gives us a plaintext character of O,” said Tess.

Jaime wrote that down as well.

COUNTESSCOUNTESSCOUNTESSC

FCHBMFWSHFUVWSXLJSMCBHWJU

DO

They went through the whole cipher like this. Once they were through, Jaime read the message out loud:

COUNTESSCOUNTESSCOUNTESSC

FCHBMFWSHFUVWSXLJSMCBHWJU

DONOTBEAFRAIDOFTHESPIDERS

“‘Do not be afraid of the spiders,’” Jaime said. “Well. That’s helpful.”

“I don’t see how that’s helpful,” Theo said. “Who’s afraid of spiders? You might as well say ‘Do not be afraid of the vacuum cleaner.’” He plucked a tiny mechanical spider from the nearest plant.

“Not everyone likes those so much,” said Jaime, watching the little robot leap back into the plant and scurry up the stalk.

“You don’t have houseplants?” Theo asked.

“Mima likes to prune her own plants.”

Tess said, “Forget about the spiders and the houseplants for a minute. Let’s back up. Maybe we were on the right track yesterday when we thought the clue was in the text of the letter Ada wrote. Remember, someone bothered to cover up the whole thing, not just the ciphertext.”

“It was easier to cover up the whole thing rather than a little part of it,” Theo said absently, but he stuck his hand in his bushy hair and held it there, his thinking pose.

Jaime turned the pages in his sketchbook to the text of the letter he had copied. “She says that she can imagine the puzzle displayed in a museum. One more relic among many.”

“The Morningstarrs set these clues back in 1855. Old things end up in museums. At least, old things that aren’t streets or graves or entire buildings end up in museums.”