And if that plan had failed, they would have tried something else. And even if all the plans had failed, they would have failed after, not during the breach.

No matter how bad the incongruity was, the continuum should have tried to prevent it. Instead, it had added nine minutes’ slippage, nine minutes that had sent Verity through at the exact moment to save the cat, when five minutes either way would have prevented it from happening at all. It was as if the continuum had taken one look at the incongruity and fainted dead away, like Mrs. Mering.

Verity had said to look for the one little fact that didn’t fit, but none of it fit: Why, if the continuum was trying to repair itself, hadn’t it sent me through at Muchings End so I could have returned the cat before Mrs. Mering went off to consult Madame Iritosky? Why had it sent me through three days late and just in time to prevent Terence from meeting Maud? And the biggest little fact of all, why had the net allowed the incongruity at all when it was supposed to shut down automatically?

“You understand these are all hypothetical scenarios,” TJ. had said. “In all these cases, the net refused to open.”

It was impossible to get anywhere near Waterloo. Or Ford’s Theater. Or Franz-Joseph Street. If the cat was so pivotal to the course of history, why wasn’t it impossible to get anywhere near Muchings End? Why wasn’t there increased slippage on Verity’s drop, where it was needed, and so much in Oxford in April, 2018? And how, if the slippage was keeping everything away, had I gotten through?

It would have been nice if the answer had been there, in the lab in 2018, but it was obvious that, whatever had caused the slippage, it wasn’t anything Jim Dunworthy or Shoji Fujisaki had done. They weren’t doing any drops.

Doubtless, if Hercule Poirot were here, he’d have come up with a neat solution not only to the Mystery of the Baffling Incongruity, but also that of the Little Princes in the Tower, Jack the Ripper, and who blew up St. Paul’s. But he wasn’t, and neither was the dapper Lord Peter Wimsey, and if they were, I’d have taken their coats away from them and put them over my knees.

Somehow, during that reverie, I had realized I was staring at an unevenness in the pitch-blackness opposite that might be the mortar between the stones, and that it meant light was coming from somewhere.

I flattened myself against the wall, but the light, or, rather, very slight absence of darkness, didn’t flicker or grow, like a torch coming down from somewhere above.

And it wasn’t the reddish-yellow of a lantern. It was only a grayer shade of black. And I must really be time-lagged, because it took another five minutes for the other possibility to occur to me: that the reason for the pitch-blackness was that it was night and I was in a tower, after all. And the way out was down.

And a near-fall and scraping of my right hand catching myself to realize that if I waited another half hour I’d be able to see where I was going and get out of here without killing myself.

I sat back down on the step, leaned my head against the wall, and watched the grayness grow.

I had made an assumption that darkness meant a dungeon, and as a consequence, I had been looking at things all wrong. Was that what we were doing in regard to the incongruity, too? Had we assumed something we shouldn’t have?

History was full of mistaken assumptions — Napoleon’s assuming Ney had taken Quatre Bras, Hitler’s assuming the invasion would come at Calais, King Harold’s Saxons’ assuming William the Conqueror’s men were retreating instead of leading them into a trap.

Had we made a mistaken assumption about the incongruity? Was there some way of looking at it which explained everything — from the lack of slippage on Verity’s drop to the excess of it in 2018? Some way of looking at it in which everything fit — Princess Arjumand and Carruthers and the bishop’s bird stump and all those bloody jumble sales and curates, to say nothing of the dog — and it all made sense?

I must have fallen asleep, because when I opened my eyes, it was fully daylight and there were voices coming up the stairs.

I looked wildly round the narrow tower, as if there might actually be somewhere to hide, and then sprinted up the stairs.

I had gone at least five steps before I realized I needed to count the steps so I would know where the drop was. Six, seven, eight, I counted silently, rounding the next curve of the steps. Nine, ten, eleven. I stopped, listening.

“Hastyeh doon awthaslattes?” the woman said.

It sounded like Middle English, which meant I’d been right about this being the Middle Ages.

“Goadahdahm Boetenneher, thahslattes ayrnacoom,” the man said.

“Thahslattes maun bayendoon uvthisse wyke,” the woman said.

“Tha kahnabay,” he said.

I couldn’t understand what they were saying, but I had heard this conversation a number of times before, most recently in front of the south door of St. Michael’s. The woman was demanding to know why something wasn’t done. The man was making excuses. The woman, who must be an early ancestor of Lady Schrapnell’s, was saying she didn’t care, it had to be done in time for the jumble sale.

“Thatte kahna bay, Goadahdahm Boetenneher,” he said. “Tha wolde hahvneedemorr holpen thanne isseheer.”

“So willetby, Gruwens,” the woman said.

There was a clank of stone on stone, and the woman snapped, “Lokepponthatt, Gruwens! The steppe bay lossed.”

She was yelling at him for the loose step. Good. I hoped she read him out properly.

“Ye charge yesette at nought,” she said.

“Ne gan speken rowe,” the workman said placatingly.

They were still coming up. I looked up the tower’s shaft, wondering if there might be a room or a platform above.

“Tha willbay doone bylyve, Goadahdahm Boetenneher.”

Botoner. Could the woman be Ann Botoner, or Mary, who had built the spire of Coventry Cathedral? And could this be the tower?

I started up again, trying not to make any noise and counting the steps. Nineteen, twenty.

There was a platform, overlooking an open space. I looked down at it. The bells. Or where the bells would be when they were installed. I had just ascertained my space-time location. It was the tower of Coventry Cathedral, the year it was built. 1395.

I couldn’t hear them. I went back to the stairs and took two tentative steps down. And nearly ran into them.

They were right below me. I could see the top of a white-coiffed head. I leaped back up to the level of the platform, and on up the stairs, and nearly stepped on a pigeon.

It squawked and flew up, flapping like a bat at me and then past me and down onto the platform.

“Shoo!” Dame Botoner shouted. “Shoo! Thah divils minion!”

I waited, poised for flight and trying not to pant, but they didn’t come any farther. Their voices echoed oddly, as if they had gone over to the far side of the platform, and after a minute I crept back down to where I could see them.

The man was wearing a brown shirt, leather leggings, and a pained expression. He was shaking his head. “Nay, Goadudahm Marree,” he said. “It wool bay fortnicht ahthehlesst.”

Mary Botoner. I looked wonderingly at this ancestor of Bishop Bittner’s. She was wearing a reddish-brown shift, cut out in the wide sleeves to show a yellow underdress, and fastened with a metal belt that sank somewhat low. Her linen coif was pulled tight around her plump, middle-aged face, and she reminded me of someone. Lady Schrapnell? Mrs. Mering? No, someone older. With white hair?

She was pointing to things and shaking her head. “Thahtoormaun baydoon ah Freedeywyke,” she said.

The workman shook his head violently. “Tha kahna bay, Goaduhdahm Boetenneher.”