"No, I know it was. They told me," she said, and at Mr. Dunworthy's doubtful look, "You forget, it only happened seven months ago as far as they're concerned, not fifty years. They don't know it was you they ran into, though. How long did you stand there, speaking to them and the guard?"

"Five minutes, perhaps. Not long."

"But long enough that if they'd told you straight out where you were instead of trying to get money out of you, you wouldn't have collided with the Wren." She leaned forward. "On the night we were looking for John Bartholomew, Eileen saw him and ran after him, but she wasn't able to catch him because Alf and Binnie jumped in front of her. And they were what kept her from going back to Oxford on the last day of her assignment."

"I don't understand. You think Alf and Binnie are somehow responsible for that, and for what I did? That it's their fault and not mine? But if I hadn't come through, if I hadn't decided to go see St. Paul's, it wouldn't have happened."

"Exactly," Polly said. "Listen. Because they kept Eileen from going back through to Oxford, she was there to save their lives at least once and possibly more than that." She told him about the measles and the City of Benares.

"And they repaid her by keeping her from catching John Bartholomew?"

"Yes," Polly said eagerly. "And because they delayed her, when she did go after him she was waylaid by a fire captain and forced into driving a bombing victim to St. Bart's. She saved that bombing victim's life, and Mike saved Hardy's life, and last night I saved Sir Godfrey's."

"And you think those people went on to do something important in the war?" Mr. Dunworthy asked. "What?"

"I don't know. Perhaps someone went to see the pantomime Sir Godfrey's going to put on, and their house was bombed while they were at the theater. Or your Wren's RAF plotting saved some pilot's life, and he went on to do bombing runs over Berlin. Or the naval officer who stopped to help your Wren torpedoed a U-boat or captured the Enigma codebooks or sank the Bismarck. Or one of them affected someone else who did something. We know Hardy brought back five hundred and nineteen soldiers from Dunkirk. And those soldiers could each have-"

"And you think this is all part of some grand plan?"

"Yes. No. Not a plan, but ... the thing is, it wasn't an accident that I was performing at the Alhambra, and it wasn't an accident that Sir Godfrey was at the Phoenix." She told him about her shoe and ENSA and Mrs. Sentry at the Works Board seeing her in A Christmas Carol and what Sir Godfrey had told her about his decision not to join the touring company and go to Bristol.

"I was able to save his life because I was here, because none of our drops would open. I think we may have been wrong about why they're not opening, and about the slippage. What if it's not to prevent us from altering the course of history? What if it's to put us where we can? To keep us here until we do?"

She reached forward and took his hands in hers. "What if by colliding with the Wren, you saved her life instead of causing her death? What if she was on the way to meet the Wren who was killed, and because you delayed her, she wasn't there when the bomb hit? Or what if you saved the life of the naval officer? Or the man in the black suit? Was he going toward St. Paul's or coming from it?"

"Toward St. Paul's."

"Then he might have been a member of the fire watch going on duty, and on the twenty-ninth he found one of the incendiaries and put it out, and if you hadn't run into him, St. Paul's would have burned down. And Alf and Binnie were what made you run into him."

"But-"

"Mike saved Private Hardy's life because the slippage caused him to arrive in Saltram-on-Sea too late for the bus. And I met Sir Godfrey because the net sent me through in the evening instead of the morning." She told him about being caught by the warden and taken to St. George's. "And because of the slippage that first time you came through, you ended up at St. Paul's Station. Where you needed to be to run into the Wren."

"So you're saying slippage's function is to bring about alterations, not prevent them? That it kept us here intentionally?"

"I know what you're going to say, that a chaotic system isn't a conscious entity-"

"That's exactly what I'm going to say."

"But it wouldn't have to be. You thought the shutting of our drops was a defense mechanism. Perhaps it is, only not to shut off interference from the future, but to enlist it when the continuum's threatened. If Hitler'd won the war, he'd have had time to develop the atomic bomb, and he wouldn't have hesitated to use it against the United States and all the other non-Aryan peoples. He already had a plan in place for wiping out Africa's 'mud people,' and he wouldn't have stopped there. He could have ended by wiping out-"

"Everything," Mr. Dunworthy said. "Gotterdammerung, the twilight of the gods. But if that's the case, and the continuum wanted to protect itself, why didn't it simply let us come through and shoot Hitler?"

"I don't know. Perhaps the system only allows minor changes. Or unintentional ones. Or perhaps something else is going on in those divergence points which makes it impossible to alter them. Or perhaps we came into the picture too late. Like the Good Fairy in Sleeping Beauty-"

"The Good Fairy?"

"Yes," she said earnestly. "She couldn't undo the spell, she could only make it less terrible. Time travel wasn't invented till long after the start of the continuum. Perhaps we're too late to completely repair it, but we can still-"

"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."

"But you think whatever that action was, one of us did it," Mr. Dunworthy said. "And it was one of us who won the war."

"No," she said, frustrated. "I'm not saying that either. No one person or thing won the war. People argue over whether it was Ultra or the evacuation from Dunkirk or Churchill's leadership or fooling Hitler into thinking we were invading at Calais that won the war, but it wasn't any one of them. It was all of them and a thousand, a million, other things and people. And not just soldiers and pilots and Wrens, but air-raid wardens and planespotters and debutantes and mathematicians and weekend sailors and vicars."

"Doing their bit," Mr. Dunworthy murmured.

"Yes. Canteen workers and ambulance drivers and ENSA chorus girls. And historians. You said no one can be in a chaotic system and not affect events. What if your-our-coming to the past added another weapon to the war, a secret weapon like the French Resistance or Fortitude South?"

"Or Ultra."

"Yes," Polly said. "Like Ultra. Something which operated behind the scenes, and which, combined with everything else, was enough to avert disaster, to tip the balance."

"And win the war," Mr. Dunworthy said softly.

There was a long silence, and then he said, almost longingly, "But there's no proof ..."

No, she thought, except that so many lives saved and so many sacrificed- so much courage, kindness, endurance, love-must count for something even in a chaotic system.

"No," she said. "I haven't any proof."

There was a knock, and Eileen leaned in the door, her red hair windblown and her cheeks rosy. "What are you two doing sitting here in the dark?" she said, and switched on the light. "You look as if you could both do with some tea. I'll put the kettle on."

"No, wait," Polly said. "Did you find out who the man you saved was?"

"Yes." She took off her hat. "The admitting nurse wouldn't tell me anything, and neither would the matron, so then I hit on the idea of going to the men's ward and telling the nurse that Mrs. Mallowan had sent me to find out."

"Mrs. Mallowan?" Mr. Dunworthy said.

"That's Agatha Christie's married name." She unbuttoned her green coat. "The nurse and I chatted a bit about Murder in the Calais Coach, and I told her about Agatha Christie's new book, which hasn't come out yet. It's all right, Polly, I told her I had an editor friend who'd let me look at it. And as a result, she let me look at the ambulance log."

"And the man you saved was-?"

"There were three people, actually, or at any rate the nurse said she doubted they'd have survived if they hadn't been brought immediately to hospital. I wrote them down," Eileen said, taking a sheet of paper out of her handbag and reading from it. "Sergeant Thomas Brantley, Mrs. Jean Cuttle-that was the ambulance driver-and Captain David Westbrook."

Mr. Dunworthy made an involuntary sound.

"Do you know who Captain Westbrook is?" Polly asked him.

Mr. Dunworthy nodded. "He was killed on D-Day, after single-handedly holding a critical crossroads till reinforcements arrived."

For there is nothing lost that may not be found, if sought.

-EDMUND SPENSER, THE FAERIE QUEENE London-Spring 1941 "SO YOU'RE TELLING ME ALF AND BINNIE ARE WAR HEROES?" Eileen said after Polly and Mr. Dunworthy had explained Polly's theory to her.

"Yes," Polly said. "You were right about their being a secret weapon. Only they're on our side. Their jumping out in front of you when you were chasing John Bartholomew and delaying you was what was responsible for your being forced into driving the ambulance that night, so that you were able to save Captain Westbrook's life-"

"And they delayed the train."

"Train?" Polly said.

"When we came to London. They chased a headmistress out of our compartment, and she tried to have us thrown off the train, and it made us late leaving the station. And later we found out the railway bridge ahead of us had been bombed, and Alf said, 'It was a good thing we was late.' " She looked up at Polly wonderingly. "They saved my life. And the headmistress's."

"And you saved Captain Westbrook's."

"And you two and Mike and I won the war?" Eileen said.

"Helped to win the war," Mr. Dunworthy said. "Tipped the balance."

"But I don't understand. If they'd lost the war before we came, then how could you have been at VE-Day? There wouldn't have been a VE-Day, would there?"

"Yes," Polly said, "because by 1945, you'd already saved Captain Westbrook's life and I'd already saved Sir Godfrey-"

"But you hadn't done that when you were at VE-Day," Eileen said, hopelessly confused. "You hadn't even come to the Blitz yet."

"Yes, I had," Polly said patiently. "I came to the Blitz in 1940, and I went to Trafalgar Square on VE-Day five years later, in 1945."

"But what about all those years before any of us came here, before time travel was even invented? The war was lost then, wasn't it?"

"No," Polly said. "It was always won because we had always come. We were always here. We were always a part of it."

"The past and the future are both part of a single continuum," Mr. Dunworthy said, and launched into a long and involved explanation of chaos theory.

"But I still don't understand-"

"Don't understand what?" Binnie asked, coming in and announcing that from now on she wished to be called Florence-"Like Florence Nightingale"-and become a nurse, which put an end to the conversation.

But the next morning after Alf and Binnie had gone to school, Eileen brought up the subject again. "So because Mr. Dunworthy ran into the Wren and Mike untangled the propeller and you saved Sir Godfrey, it changed things just enough that we won the war, is that right?"

"Yes," Polly said.

"Then there's no reason to keep us here," she said, "and we can go home."

"Eileen-"

"Mr. Dunworthy, you said every historian who's come here has altered events, and they all went back to Oxford. And after you ran into the Wren, you went back to Oxford. So now that we've done what we were supposed to do, they should be able to come and fetch us, shouldn't they? Or our drops should begin working again." She looked expectantly from Polly to Mr. Dunworthy and back again. "We need to go check them."

"I'll go to the drop in St. Paul's this morning," Mr. Dunworthy promised.

But after Eileen had elicited a promise that Polly would check her drop on her way to the theater and had left to drive General Flynn, he said to Polly, "She may, of course, be right about the drops-"

"But if she were, Colin would already be here."

"Yes," he said, "and the fact that he isn't very likely means our part in this is not over."

"I know," Polly said, thinking of how Major Denewell had told her and the other FANYs the war could still be lost even during that last year.

"More may be required of us before the end," Mr. Dunworthy told her.

Including our lives, Polly thought.

She had nearly died rescuing Sir Godfrey. The next time she might not make it. Like the countless rescue workers and ARP wardens and firemen who'd died digging people out of the rubble or taking people to shelter or defusing bombs. Or she might simply be killed outright by an HE, as Mike had been, and all the other people who'd died in the Blitz and in hospitals and prison camps and newspaper offices. Casualties of war.

But still even in death, doing their bit. Like Mike. It was his death that had made her go to the Works Board and volunteer to be an ambulance driver and be assigned to ENSA and save Sir Godfrey.

"I know there's a good chance we won't make it back," she told Mr. Dunworthy, and as she did, it struck her that that was what soldiers said when they were leaving for the front.

"But it doesn't matter," she said, and meant it. "All that matters is that Sir Godfrey didn't die and I'm not responsible for losing the war, and that I can see Miss Laburnum and Doreen and Trot without getting them killed. And if I'm killed, I won't be the only one to die in World War Two. I'm only sorry I got you into this."

"We got each other into it. And we may yet get out."

"And if not, we still stopped Hitler in his tracks." She smiled at him.

"We did indeed," he said, and looked suddenly years younger. "And we, like St. Paul's, are still standing, at least for the moment. Speaking of which, when I go there to check the drop, I intend to ask to be taken on as a volunteer. I have always wanted to serve on the fire watch and help save St. Paul's-"