“And what’s to stop you from enlisting the moment you get there? Or haring off to London to see Polly Churchill?”

“That’s the last thing I’d do,” Colin said fervently, and Dunworthy wondered what that was all about. Had she laughed at him and hurt his feelings? “And I promise I won’t enlist. I’ll swear to it if you like. Or sign an oath in blood or something.”

“No.”

“But I’ve found a farm in Hampshire where there wasn’t a single bomb or V-1 for the entire war. And I’ve researched milking cows and gathering eggs—”

They’d reached the lab. Dunworthy stopped outside the door. “I am not sending you anywhere until you have passed your examinations, been admitted to Oxford, and completed your undergraduate degree—none of which look likely at this point.”

“That’s unfair. I rewrote my essay on Dr. Ishiwaka and got high marks on it, even though I still think his theory’s rubbish.”

And let’s hope you’re right, Dunworthy thought. “Run along,” he said. “I have business to conduct.”

“I don’t mind waiting.”

“There’s no point. I do not intend to change my mind. And in case you were hoping to sneak into the drop with me the way you did when I went after Kivrin Engle, I am not here to use the net. I am here to talk to Badri.”

“Then there’s no need to bar me from the lab, is there?” Colin said, sidling in before Dunworthy could shut the door. “I’ll wait till you’re done and then tell you my other idea. You won’t even know I’m here.”

“See that I don’t,” Dunworthy said, and started over to Badri, who was at the console.

“If you’re here about your drop to St. Paul’s,” Badri said, “we just finished calculating the coordinates, so you can go at any time.”

“Good,” Dunworthy said. “I want to see the slippage for this week’s drops. Is the amount still increasing?”

“Yes.” Badri called it up on the screen. “But the rate of increase is less than last week.”

Good, Dunworthy thought. Perhaps it was only a temporary anomaly.

“I’ve been looking at the individual drops,” Badri said. “The elevated slippage seems to be confined to drops back to World War II, so the increase could be due to the greater incidence of divergence points wars produce. Or to wartime conditions—civilian observers, ARP patrols, that sort of thing.”

But scores of historians had gone to World War II over the years, and there’d been no increase in the average slippage. “Have all the historians I spoke to you about been canceled or rescheduled?”

“Yes, sir,” Badri said, and Linna handed him a list.

“What about Michael Davies?” Dunworthy asked, looking at it.

“We rescheduled him to do his Dunkirk evacuation observation first. He left”—he consulted the console screen—“four days ago. He’ll be back six to ten days from now.”

“And the Pearl Harbor drop’s scheduled for when?”

“The end of May.”

Good, Dunworthy thought. I’ll have six weeks before I need to make a decision. “Why the uncertainty in when he’ll return? Was the projected slippage high?”