Dr. Little Crow walked them to room 319 and unlocked the door with a key card. She opened the door and turned on the lights. It was a medium-sized room with various shelves and filing cabinets around the perimeter, and a round table with some chairs in the center. A portrait of Ada Lovelace hung over one of the filing cabinets. Dark curls framed her face. Hooded eyes seemed to stare at him.

“She was only thirty-six when she died,” said Dr. Little Crow, when she saw where Theo was looking. “And she had been really ambitious, too. She saw more potential for Charles Babbage’s designs than he did.” She bent and let Nine sniff her hand before scratching the cat between the ears. “Okay, Kitty, you stay right here while I get these guys set up.” Nine sat and stared peacefully into the middle distance as if that had been her plan all along.

The librarian entered the room and pulled a binder off the shelf. She opened the binder on the table and paged through the plastic-covered letters until she came upon what she was looking for. “The King–Babbage letters begin right here. You can have a seat and examine them for as long as you want.”

“Thank you!” said Tess.

“No problem,” said the librarian. “I’ll be at the desk with your kitty.”

“Her name is Nine,” Tess told her.

“Is it?” Dr. Little Crow said. “What a great name!” To the cat, she said, “Come on, you beautiful thing. I’m sure I can scavenge up some treats for you. Crows are good at that.” She laughed at her own joke and closed the door behind her, leaving Theo, Tess, and Jaime alone with the Countess of Lovelace.

A mathematician called “Countess.”

It was still funny.

Maybe one day he’d marry a librarian.

“Theo, are you going to stand there daydreaming about Dr. Little Crow or are you going to help us look at these letters?” Tess said.

Theo sat down at the table. There were six letters in total, all sent between 1843 and 1844. They took turns reading the letters out loud, taking notes and pictures, trying to figure out if there were any hidden messages or codes.

“It is an omission not to have sent me the drawings to which continual reference is made throughout your packet of papers . . . ,” the first one began.

Then: “The solution was (as you supposed) of the simplest description.”

“I have just told Weatstone that I cannot consent to your making the reuse of the remaining notes. So send them to me at once, pray.”

“In consequence of the enclosed, I am starting for Town; & I shall send this to you immediately on my arrival . . .”

“We are quite delighted at yr (somewhat unhoped for) proposal, this mor.g received. . . .”