“But even if that’s true, and even if you saved Sir Godfrey’s life and Mike saved Hardy’s and I saved the Wren’s, we still altered events, and history’s a chaotic system where a good action, done with the best intentions, can have the opposite effect. How can you be certain that even if the continuum intended us to make repairs, we did? That we didn’t make things worse instead?”

“Because they were already worse.”

“Worse? What do you mean?”

“I mean, what if we’ve been looking at the war the wrong way round? What if the disaster had already occurred, and the outcome we were altering was a bad outcome?”

“A bad outcome?” Mr. Dunworthy said, bewildered.

“Yes. What if the Allies lost the war? You said there were dozens of times when the outcome balanced on a knife’s edge, like in that old saying, ‘For want of a nail, the shoe was lost, for want of a shoe—’ ”

“—the horse was lost.”

“Yes, and because of that, the rider and the battle and the war were lost. There were scores of times in World War Two like that, when if things had gone even slightly differently, we’d have lost. Well, what if we did lose?” she asked. “What if your Wren was killed in Ave Maria Lane and Sir Godfrey was killed in Bristol and Eileen’s bombing victim died in the back of the ambulance because they couldn’t find a driver and Hardy ended up in a German POW camp and they lost the war?”

“But then time travel would never have been invented. Ira Feldman—”

“No, because the continuum’s a chaotic system, which means time travel was already a part of it, and they hadn’t lost it. Because you’d come and run into a Wren and set a cascade of events in motion. And Mike was part of that cascade, and our being stranded here.”

“We’re the horseshoe, in other words.”

“Yes—”

“And you’re saying we waltzed in, tightened a few nuts and bolts, and won the war?” Mr. Dunworthy said. “Historians as Little Miss Fix-Its? My dear, history’s a chaotic system. It’s far more complicated than—”

“I know it’s complicated. I’m not saying we won it. And I’m not saying your Wren or Hardy or Sir Godfrey or Alf and Binnie or whoever it is they and Eileen treated on the twenty-ninth was who won it either. Or even that saving them was what tipped the balance. It may have been something else altogether—Marjorie’s deciding to become a nurse, or one of the FANYs I worked with borrowing my dance frock, or Mike’s nearly colliding with Alan Turing. Or something we don’t even know we did—our stepping ahead of someone onto an escalator or hailing a taxi or asking for directions. Mike might have done something in hospital, or Eileen might have affected one of her evacuees. Or I might have taken too long to wrap a customer’s parcel and delayed her five minutes, so that she missed her bus, or got caught in the tube when the sirens went.”