“And I’m not sure the project’s called Ultra at this point. ‘Ultra’ stood for ultra-top-secret, the most classified category of military secrets, and I think in 1940 the project may just have been called Enigma, and not—”

“It doesn’t matter what it’s called. I have no intention of mentioning Enigma or Ultra. I intend to find Gerald and get out.”

“There’s the boarding call,” Eileen said. “Perhaps you’ll be in the same compartment with someone who works there, and you can ask them if they know Gerald and how you can get in touch with him, and you won’t need to go to Bletchley at all.”

Jesus, he hadn’t thought about running into them on the train. “What does Turing look like again?” he asked Polly.

“Blonde hair. Stammer.”

“And Dilly Knox is tall and smokes a pipe.”

“And has a limp like yours. And Alan Ross has a long red beard, and when it’s cold wears a blue snood over it.”

“Over his beard?” Mike said. “And you’re worried about me being conspicuous? They sound crazy.”

“Eccentric,” Polly said. “Oh, and Ross has a little boy, and when he traveled, he doped him with laudanum—”

“Laudanum,” Eileen said wistfully, and when they looked at her, she explained, “Sorry, I was just thinking how useful laudanum would have been on that journey to London with the Hodbins.”

“Yes, well, I don’t know if Ross’s son was a terror or not,” Polly said, “but he gave him laudanum and stowed him in the luggage rack, so if you see a little boy sleeping up in the luggage rack, you’ll know that’s the compartment Alan Ross is in.”

And I can make sure I keep out of it. “Look, I’d better get out to the platform,” he said.

“Wait,” Eileen said, grabbing his sleeve. “What happened?”

“What happened?” he repeated blankly.

“To Ross’s son?” Polly asked.

“No, to Shackleton. When he left his crew on the island and went off to get help. Did he come back?”

“Yes, with a ship, to take them all home. He didn’t lose a single man.”

“Good,” she said, and smiled at him.

“Ring us as soon as you get there,” Polly said.

“I will,” he promised, thinking, If I can get there. Just because he’d gone to one divergence point didn’t mean the continuum would let him near another, especially one where a single person could mess up everything. His train could be blown up en route. Or the train might be too crowded to get on, which looked like it was going to be the case.

It was packed to the gills, but he managed to squeeze on, and on the train from Oxford, he was even able to find a seat—taking care to pick a compartment that didn’t have any blonde stammerers, tall pipe-smokers, or doped-up children in it. He picked one occupied by five soldiers and two elderly ladies. He slung his bag up onto the luggage rack—which only held brown-paper-wrapped packages, no children—and sat down in the single empty seat.