That afternoon, back at the Byron house, Ada sat propped up in bed, having been ushered there by Mrs. Woolcott, Mrs. Somerville, Anna, and Mary, with instructions to stay put.

Beside her lay a box of pencils, a compass, and a ruler. There were even a few scraps of paper, two books, and a discarded shawl on the floor.

Mrs. Somerville had come up to say her last thank-yous and goodbyes to an Ada already lost in her book, and she gave Mary a wink as she left.

Ada looked up when the door clicked. “You did it, Mary. You uncovered the secrets.”

“Only with the dates that you left me,” deferred Mary. “And you found the will!”

“Together, then,” Ada said.

“Together, all of us,” said Mary. Ada grimaced, but she had to admit that Allegra and Jane had proved themselves useful.

“And yet…,” said Ada.

“Yet what? Have I missed something?”

“So you found out,” Ada asked, “how Bubbleburst knew there was a missing twin? And how he found Alice? The Jamaica connection? And how he was connected to Sir Caleb? And why he had the same kind of tattoo on his arm as the fishmonger from our first case?”

Mary froze for a moment, stunned. She hadn’t found out any of these things. She didn’t even realize they were questions that needed answering.

But they did remind her of another lingering question that perhaps could be answered.

She hurried downstairs, eager to catch Mrs. Somerville before her carriage departed, but was momentarily distracted by the sight of Peebs, outside in the rain, seeing to a very large crate being swung by a crane from a wagon onto the doorstep of the Marylebone house, with two soggy workmen trying their level best to mind their language. She went to investigate.

“Peebs, what in heaven is this?” Mary asked.

“This? Something I arranged after the…er…incident with the balloon. It’s finally arrived. Quicker than I thought, to be honest.”

“What could it possibly be?”

“A surprise, although if you tell her, it might cheer her up. It’s a steam engine, for Ada’s next balloon. I thought it might be useful if she could, well, steer the next one. That and keep it aloft without anyone having to leap out of it midair.” He laughed.

Mary clapped her hands in delight—the device would indeed rouse Ada’s spirits. But she still had one burning question to ask, and Mrs. Somerville was climbing aboard the carriage.

“Mrs. Somerville! Mrs. Somerville! If you have a moment!” Mary ran into the street, taking care to dodge the crane and the crate and the wagon and the workmen.

“Of course, Miss Godwin, what is it?”

“You referred to Ada as the second cleverest girl in England.”

“That’s right, yes. We often do, Mr. Babbage and I. She’s terribly clever, your Ada.”

“She is, of course she is. But then—who is the cleverest girl in England?”

Mrs. Somerville’s smile faded, and Mary almost thought she saw her shiver.

“That would be Nora Radel.” She paused. “May you never meet.”