“That’s why you had Verity do drops in May?” I said. “Because you think the incongruity may have attempted to adjust itself before it happened?”

“But we haven’t found any slippage anywhere except for your drop,” he said, sounding frustrated. “Every one of these,” he waved at the screen, no matter how large or how small the self-correction, has the same basic pattern: radically increased slippage at the site, moderately increased slippage in the immediate area, and then isolated pockets of slippage farther from the site.”

“Which doesn’t match our incongruity at all,” I said, staring at the screen.

“No,” T.J. said, “it doesn’t. The slippage on Verity’s drop was nine minutes, and I haven’t been able to find any radical increase in slippage anywhere near the site. The only slippage at all is the cluster in 2018, and it’s much greater than it should be, that far from the site.”

He went to the comp, typed something in, and came back to the left-hand screen, which had changed slightly. “The only one that’s been close is this one,” he said. “We had the historian fire an artillery shell that killed Wellington.”

He felt in his pockets for the lightpen, couldn’t find it, and settled for his finger. “See this? Here and here, you have radically increased slippage, but it can’t contain the altering events and discrepancies which develop here and here and here,” he said, pointing at three spots close to the focus, “and the amount of slippage drops off sharply here, and you can see here,” he pointed farther out, “the backups start to fail, and the net begins to malfunction as history starts to alter course.”

“And Napoleon wins the battle of Waterloo.”

“Yes,” he said. “You can see the parallels to your incongruity here,” he pointed at darker gray, “where there’s a pocket of increased slippage nearly seventy years from the site, and here,” he pointed at a spot of lighter gray, “in the lack of slippage at a short distance from the site.”

“But there’s still radically increased slippage at the site,” I said.

“Yes,” he said grimly. “In every single incongruity we’ve tried. Except yours.”

“But at least you’ve been able to prove that incongruities are possible,” I said. “That’s something, isn’t it?”

“What?” he said blankly. “These are all just mathematical sims.”

“I know, but you’ve shown what would happen if—”

He was shaking his head violently. “What would happen if we really tried to send an historian to Waterloo to intercept a message or shoot a horse or give directions is that the net wouldn’t open. Historians have been trying for over forty years. No one can get within two years and a hundred miles of Waterloo.” He waved angrily at the banks of screens. “These sims are all based on a net without any safeguards.”

So we were right back where we started.

“Could something have overridden the safeguards on Verity’s drop?” I said. “Or made them malfunction?”

“That was the first thing we checked. There was no sign of anything but a perfectly normal drop.”

Mr. Dunworthy came in, looking worried. “Sorry I took so long,” he said. “I went to see if the forensics expert had made any progress on either the name or the date.”

“Has she?” I said.

“Where’s the recruit?” Warder cut in crabbily before Mr. Dunworthy could answer. “He was supposed to come back with you.”

“I sent him over to the cathedral to keep Lady Schrapnell occupied so she wouldn’t come over while Ned was here,” he said.

And I trusted him to do that about as much as I trusted him to find his way home, so we’d better make this short.

“Has the forensics expert decoded Mr. C’s name?”

“No. She’s narrowed the number of letters down to eight, and she’s located the Coventry entry, and is working on the date.”

Well, that was something. “We need it as soon as possible,” I said. “Terence and Tossie got engaged yesterday.”

“Oh, dear,” Mr. Dunworthy said, and looked around as if he would have liked to sit down. “Betrothal was a very serious matter in Victorian days,” he said to T.J.

He turned back to me. “Ned, the two of you still don’t have any leads as to Mr. C’s identity?”

“No, and we still haven’t been able to get hold of the diary,” I said. “Verity’s hoping Mr. C comes to the church fête today.”

I tried to think if there was anything else I should tell or ask them. “T.J., you said something about slippage on the return drops?”

“Oh, yes. Warder!” he called across to the console, where she was violently pounding keys. “Have you figured the slippage yet?”

“I am trying to—”

“I know, I know, you’re trying to get Carruthers out,” T.J. said.

“No,” she said. “I am trying to bring Finch through.”

“It can wait,” T.J. said. “I need the slippage on Ned’s return drop.”

“All right!” she said, her seraphim’s hundred eyes flashing. She beat on the keys for half a minute. “Three hours, eight minutes.”

“Three hours!” I said.

“It’s better than Verity’s last drop,” Mr. Dunworthy said. “That was two days.”

T.J. held his hands out, palms up, and shrugged. “There hasn’t been any on any of the sims.”

I thought of something. “What day is it?”

“Friday,” T.J. said.

“It’s nine days till the consecration,” Mr. Dunworthy said, thinking. “The fifth of November.”

“Nine days!” I said. “Good Lord! And I don’t suppose the bishop’s bird stump has turned up?”

Mr. Dunworthy shook his head. “Things don’t look good, do they, Ensign Klepperman?”

“There’s one thing that does,” T.J. said, darting back to the comp and hitting keys. “I did a bunch of scenarios on the Berlin bombing.” The screens changed to a slightly different pattern of gray blurs. “Missing the target, plane getting hit, pilot getting hit, even eliminating the pilot and plane altogether, and none of them affects the outcome. London still gets bombed.”

“That is good news,” Mr. Dunworthy said wryly.

“Well, it’s something anyway,” I said, wishing I could believe it.

The net shimmered, and Finch appeared. He waited for Warder to raise the veils and then came straight over to Mr. Dunworthy and said, “I have excellent news regarding the—” He stopped and looked at me. “I will be in your office, sir,” he said and went out hastily.

“I want to know what Finch is up to,” I said. “Did you send him back to drown Princess Arjumand?”

“Drown—?” T.J. said, and started to laugh.

“Did you?” I demanded. “And don’t tell me you’re not at liberty to say.”

“We are not at liberty to tell you what Finch’s mission is,” Mr. Dunworthy said, “but I can tell you, Princess Arjumand is perfectly safe, and that you will be pleased with the results of Finch’s mission.”

“If Henry’s going back,” Warder said irritably from the console, “I need to send him now so I can start the half-hour intermittent on Carruthers.”

“We need the forensics expert’s information as soon as you have it,” I said to Mr. Dunworthy. “I’ll try to come through tonight or tomorrow.”

Mr. Dunworthy nodded.

“I don’t have all day,” Warder said. “I am trying—”

“All right,” I said, and went over to the net.

“What time do you want to be sent back to?” Warder asked. “Five minutes after you left?”

Hope suddenly leaped up like one of Wordsworth’s rainbows. “I can go back to whenever I want?”

“It’s time travel,” Warder said. “I haven’t got all—”

“Half-past four,” I said. With luck, there would be twenty minutes’ slippage, and the fête would be completely over.

“Half-past four?” Warder said, looking belligerent. “Won’t someone have missed you?”

“No,” I said. “Terence will be delighted he doesn’t have to go back to the Pony Ride.”

Warder shrugged and began setting up the coordinates. “Step in the net,” she said, and hit the “send” key.