Even good weather could affect history. The Luftwaffe’s raid on Coventry had been successful because of cold, clear weather and a full “bomber’s moon.”

Weather and its sidekick, disease. What if Professor Peddick caught cold from sleeping in the rain and had to be taken back to Oxford tomorrow? The United States President William Henry Harrison had caught cold standing in the rain at his inauguration and died of pneumonia a month later. Peter the Great had caught cold while sighting a ship and died within a week. And not just colds. Henry the Fifth had died of dysentery, and as a result the English lost everything they’d gained at Agincourt. The undefeatable Alexander the Great was defeated by malaria, and the face of the whole continent of Asia changed. To say nothing of the Black Death.

Weather, disease, changes in climate, shifts in the earth’s crust — Professor Overforce’s blind forces — all were factors in history whether Professor Peddick would admit it or not.

The problem, of course, as in so many wars, was that Professor Overforce and Professor Peddick were both right. They were just a century too early for chaos theory, which would have incorporated both their ideas. History was indeed controlled by blind forces, as well as character and courage and treachery and love. And accident and random chance. And stray bullets and telegrams and tips. And cats.

But it was also stable. I remembered distinctly T.J. saying that, and Mr. Dunworthy saying that if the incongruity had done any damage it would have shown up by now. Which meant that the cat had been returned to its original space-time location before it had caused any long-lasting consequences.

Or, the other possibility was that the cat’s disappearance hadn’t affected anything, but I knew that wasn’t true. It had made me make Terence miss meeting Maud. And I wasn’t taking any chances. I intended to return the cat to Muchings End as quickly as possible, which meant getting us on the river in the morning as quickly as possible.

Which meant it couldn’t rain. It had rained at Waterloo, turning the roads to an impossible muck and bogging down the artillery. It had rained at Crécy, soaking the archers’ bowstrings. It had rained at Agincourt.

Somewhere in the midst of worrying about the rain at the Battle of Midway, I must have fallen asleep, because I woke with a jerk to the gray light of dawn. It had stopped raining and the cat was gone.

I leaped up in my stocking feet and flung the rugs aside, trying to see if she was hidden in them somewhere, disturbing Cyril, who whuffled and rolled over.

“Cyril!” I said. “The cat’s gone! Did you see where she went?”

Cyril shot me a look that clearly said, I told you so, and subsided among the covers.

“Help me look for her!” I said, yanking the rug out from under him.

I fumbled with my shoes. “Princess Arjumand!” I whispered frantically, “Where are you? Princess Arjumand!” and she strolled into the clearing, treading daintily on the wet grass.

“Where have you been?” I said. “I should have shut you in the basket!”

She sauntered past me to the disordered bed, lay down next to Cyril, and went to sleep.

I wasn’t going to take a second chance. I got the carpetbag and emptied out the shirts and the escargot tongs. Then I got the fileting knife out of the hamper and made several short slashes in its sides with the point, making sure they went all the way through the lining. I arranged the too-small tweed jacket in the bottom for a nest and stuck the saucer next to it.

Princess Arjumand didn’t even wake up when I put her in the carpetbag and closed the clasp. Perhaps Verity was right, and she was suffering from time-lag. I jammed the clothes in the portmanteau, and rolled up all but one of the rugs, which Cyril was on.

“Rise and shine, Cyril,” I said. “Time to get up. We need to make an early start.”

Cyril opened an eye and stared at me disbelievingly.

“Breakfast,” I said, and, carrying the carpetbag, went down to the remains of the campfire. I gathered wood, laid the fire, and lit it like an old hand, and then looked through Terence’s luggage till I found a map of the river, and sat down by the fire to plot our trip.

The map was an accordion-style which folded out to portray the full winding length of the Thames, which I certainly hoped we didn’t have to cover. I had learned to read maps when I was an undergraduate, but this one suffered from a wealth of details: it not only listed villages, locks, islands, and all the distances between, but weirs, shallows, canals, towpaths, historic sights, and recommended fishing spots. I decided I’d better keep it out of Professor Peddick’s hands.

It also provided an assortment of editorial comments, such as “one of the most charming views along the river” and “a rather difficult current just here,” with the result that it was difficult to find the river in amongst all the wordage. Terence had said Muchings End was just below Streatley, but I couldn’t find either.

I finally found Runnymede, which was listed as “the historical site of the signing of the Magna Carta, not, as certain river people would have you believe, the stone on Magna Carta Island. Good bream deeps. Poor for gudgeon, dace, and jack.”

I worked my way up from Runnymede to Streatley, marked its place with my finger, and looked for Iffley. There it was: “Quaint mill, which people come from miles about to see, 12th cent. church, middling chub.” We were halfway between Iffley and Abingdon, and twenty-three miles from Streatley.

Allowing half an hour for breakfast, we’d be on the river by six. We could easily be there in nine hours, even allowing for Professor Peddick to stop along the way and send a telegram to his sister. With luck, we’d have the cat back to the place where it had disappeared by three, and the incongruity corrected by five.

“We can easily be there by teatime,” I told Cyril, folding the map up. I put it back in Terence’s bag and got eggs, a slab of streaky bacon, and the skillet out of the hamper.

The birds began to sing, and the sun came up, streaking the water and the sky with ribbons of rosy-pink. The river flowed serene and golden within its leafy banks, denying incongruities — the placid mirror of a safe, untroubled world, of a grand and infinite design.

Cyril was looking up at me with an expression that clearly said, “Exactly how time-lagged are you?”

“I didn’t get any sleep last night,” I said. “Thanks to you. Come along.”

I put the kettle on, sliced bacon, broke eggs into the skillet, and went down to the boat to wake Terence and his tutor up, banging on a pot lid with the Stilton spoon. “Time to get up,” I said. “Breakfast’s on.”

“Good Lord,” Terence said groggily, fumbling for his pocket watch. “What time is it?”

“Half-past five,” I said. “You wanted to make an early start to be at Muchings End by teatime. Miss Mering, remember?”

“Oh,” he said, and shot up out of the blankets. “You’re right. Wake up, Professor Peddick.”

“ ‘Morn, wak’d by the circling hours, with rosy hand unbarr’d the gates of light,’ ” Professor Peddick said from the stern, blinking sleepily.

I left them and ran back up to check on the eggs and the cat. She was sleeping soundly. And soundlessly, which was even better. I set the carpetbag over with the luggage and began dishing up the eggs.

“At this rate, we’ll be on the river by six,” I told Cyril, feeding him a strip of streaky bacon. “We’ll be through the lock by half-past, we’ll stop in Abingdon so the professor can send his telegram, we’ll be to Clifton Hampden by eight, Day’s Lock by nine, and to Reading by ten.”

By ten we were still in Abingdon.

It had taken us two hours to load the luggage, which seemed to have expanded, and then, at the last minute, Professor Peddick discovered his double-gilled blue chub was missing.