“Isn’t that a Rubik’s cube? I didn’t know they existed in the 1800s,” said Jaime.

“I don’t think they did,” said Theo.

Underneath the drawings, Ada had written:

The puzzle fit in the palm of my hand. Made of silver and gemstones. I believe I left it in the M.s’ drawing room. I wonder if that empty-headed little girl with the yellow hair stole it. She was clutching her reticule quite tightly when she returned to the table, if I recall.

If she doesn’t melt it down out of sheer frustration, I can imagine she will deposit it in a spare box in her attic, to be found by a descendant and displayed in some museum or another a hundred hundred years from now. One more mysterious relic among many.

Oh, we have much work to do to, Mr. Babbage. Much work.

Yours,

A.A.L.

Below the text, someone—Ada? Someone else?—had scrawled this:

FCHBMFWSHFUVWSXLJSMCBHWJU

“Does that look like the same handwriting to you?” Jaime said. “Because I’m not sure it is.”

“Someone could have added this cipher and hidden the text on the back with that second sheet of paper,” said Tess.

“But when? This collection has been here for only twenty years,” Jaime said. “And how or why would they do that?”

“That’s a good question,” said Theo.

Tess pointed to the writing. “She writes here about ‘the M.s’ drawing room.’ She has to be talking about the Morningstarrs.”

“She could be talking about anyone whose name begins with M,” Theo said.

“Come on, Theo!” Tess said. “It’s too adorable.”

“I hate when you say that.”

Jaime copied the text of the letter into his sketchbook and then took a photo for good measure. He was just slipping the phone back into his pocket when there was a brief knock on the door. Theo barely had time to close the binder before the door opened and Dr. Little Crow appeared. “How are you guys doing?” she said.

“Great!” said Jaime calmly, smoothly, innocently. “We’re almost done.”

“Whew! I think Nine’s gained nine pounds on all the treats I’ve given her. She’s napping them off now.”

“Well, Nine eats for ten,” said Tess.

Dr. Little Crow’s eyes fell on the closed binder. “You guys find anything?”

“Ada was very passionate,” Tess offered.

“She was,” agreed the librarian. “You know, I never asked you why you guys were so interested in her.”

“Isn’t everyone?” said Tess.

Dr. Little Crow laughed. “Not as many as should be! But school isn’t in session yet. Shouldn’t you be out swimming or biking or generally causing your parents grief?”