"No," he said, shivering. "There are things you don't know."

"You can tell me at home."

"No. After I've told you, you won't want-"

"Of course we'll want you," she said, truly alarmed now. "You're talking nonsense. You can tell me on the way."

"No. Now." He began to cough.

"All right," she said hastily, "but we can't do it standing out here in this freezing rain. We need to find somewhere warm. The place you've been staying, is it near here?"

He didn't answer.

He doesn't want me to know where he lives, she thought. He doesn't want me to be able to find him. Which meant at the first opportunity he intended to attempt to get away from her again. She had to get him somewhere warm before he had the chance.

But everything along Paternoster Row had burnt down the night of the twenty-ninth. She'd seen a pub off Newgate on her way home from St. Paul's that first Sunday. She'd have to hope it was still there.

It was, and thank goodness the fires, the blackout, and the weather had almost completely destroyed business. The place was all but empty. Polly sat Mr. Dunworthy, who was now shivering uncontrollably, down on the wooden settle in front of the fire, put her own coat around his shoulders, and went to the counter.

"My friend has had a bad shock," she told the middle-aged, ginger-haired barmaid. "I daren't leave him alone. Could you bring us a pot of tea?"

" 'A course, dearie," the barmaid said. "Bombed out, was he?"

"Yes," Polly said, and hurried over to the fire. Mr. Dunworthy had stood up, folded her coat over the back of the settle, and was going toward the door.

She headed him off, said, "Our tea's coming," steered him back to the settle, and draped her coat over his knees. "It'll be here in a moment."

The barmaid came out of the kitchen bearing a teapot, teaspoons, a pair of saucers, two chipped teacups dangling from her crooked fingers, and a glass full of a brown liquid. "I was bombed out meself in November," she said to Mr. Dunworthy. "Dreadful. Fair knocks the stuffin' out of you, don't it? This will do you up right."

She set the glass in front of Mr. Dunworthy. "A spot of brandy," she explained to Polly. "Nothin' like it to bring the fight back into you."

"Thank you," Polly said. She poured Mr. Dunworthy out half a cup of tea, filled it the rest of the way with brandy, and handed it to him. "There. Have some tea, and then you can tell me whatever it is. Drink it down," she ordered.

He did, and she poured him a second, but he didn't drink it, in spite of her urging. He sat staring blindly at the fire, his hands wrapped around the teacup, not as if he was warming them on it but as if he was clinging to the cup for dear life.

I need to get him home and into bed, Polly thought. And telephone to the doctor.

"Mr. Dunworthy," she said, "whatever it is you have to tell me, it can wait. Merope will have made supper, and you'll feel better after you've had a hot meal."

No response.

"You can stay with us tonight, and tomorrow we can go collect your things, and then when you're feeling better, we can decide which drop-"

"The drops won't open."

"But if the problem's the slippage-"

"The slippage was an indicator."

"We're trapped here for good, is that what you're afraid to tell me?" she said.

"Yes."

"What about Michael's roommate, Charles? Did he go to Singapore, or did you realize we couldn't get out before-?"

"No."

No. Which meant Charles would still be there when the Japanese invaded. He would be rounded up with the rest of the British colonials and herded off to a jungle prison camp to die of malaria or malnutrition. Or worse.

"What about the other historians with deadlines?" she asked.

"You're the only one. I'd pulled out all the others. I didn't realize you'd done the 1944 segment of your assignment first. That's why you weren't pulled out when the others were."

"And there's no way we'll get out before our deadlines?"

"No," he said. But there was no relief in his voice at having told her. Which meant there was worse to come. And if it wasn't Colin, there was only one thing it could be.

"The reason we're trapped," she said, "it's because we altered events, isn't it?"

He nodded.

So Mike had been right.

"How did you find out?" Mr. Dunworthy asked.

"Mike-Michael-saved a soldier's life at Dunkirk, and the soldier went back across and brought home more than five hundred others, and Michael couldn't see how that couldn't have caused changes, so we began looking for discrepancies."

"And did you find them?" he asked.

"None that I could determine for certain were discrepancies," Polly said, "but Michael wasn't the only one who'd done something. Eileen-Merope-stopped two of her evacuees from sailing on the City of Benares, and I was responsible for a shopgirl's being injured and nearly killed. But we didn't know it was possible to alter the course of events. We thought the slippage kept historians from-"

Mr. Dunworthy shook his head. "We were wrong about the slippage's function. It wasn't a line of defense guarding against damage we might do to the continuum. It was a rearguard action against an attack that had already happened-an attempt to hold a castle whose walls had already been breached."

"By time travel," Polly said.

"By time travel. And in most cases over the years, the defenses were sufficient to hold the castle. But not all. It couldn't hold it against multiple simultaneous attacks or in instances where the breach was at a particularly vital spot-"

Like Dunkirk, Polly thought. Or the autumn of 1944, when the lightest touch of a Spitfire's wing on a V-1's fin could change who lived and who died.

"Or in instances where the initial breach was too great," Mr. Dunworthy was saying. "In those cases, no amount of slippage would have been sufficient to prevent the enemy from breaking through, so the only thing the continuum could do was to attempt to isolate the infected area-"

Like Eileen's quarantine.

"-and attempt to repair the damage."

"To shut down access to the past," Polly said, "which is what you think the continuum did."

He nodded. "Trapping you here."

And you. "I'm so sorry, Mr. Dunworthy."

He shook his head. "You are not to blame."

"But if I'd told you I'd done the rocket attacks first," she said. "I knew you were canceling drops and changing schedules, even if I didn't know the reason. I was afraid you'd cancel mine, so I didn't report in, and I made Colin promise he wouldn't tell you."

He nodded as if he wasn't surprised. "Colin would do anything for you," he said.

"Oh, this is all my fault! If I hadn't made him promise, if I'd reported in, you wouldn't have let me come. You wouldn't have had to come after me-"

"No, you don't know the whole story," he said, putting up his hand to stop her. "There was an increase in slippage even before you went to 1944, but it wasn't large, and I didn't think it was serious. The amount of slippage had often been greater than the circumstances seemed to merit, and at other times far less, and I thought there was a simpler explanation than the one Ishiwaka had arrived at, even after he showed me his equations. I certainly didn't see any need to pull out my historians and shut down all time travel. I thought canceling the drops of historians with deadlines and putting the others in chronological order was sufficient till I had more data, but Dr. Ishiwaka was right. I should have pulled you all out."

"But you couldn't have known what the increase meant-"

"Dr. Ishiwaka had told me exactly what it meant, but I refused to believe him. We'd been traveling to the past for forty years without incident. I found it impossible to believe that we were a danger to the course of history. I should have listened to him. If I'd pulled you out, Michael Davies would still be alive, and you and Merope-"

"Merope?" she said, alarmed. "She doesn't have a deadline. This was her first assignment. Wasn't it?"

"Yes," he said, and she knew there was still more.

"The shutdown might not be a result of the continuum's attempt to correct itself," he went on. "It might be some sort of reflexive response to the damage, like shock in a trauma patient. And even if it is an attempt at self-correction, there's no guarantee it will be successful. The damage may be too great or too widespread to be repairable."

"But it's not," Polly said. "We didn't lose the war. I was at VE-Day-"

"That was before Michael saved the soldier, and you and Merope-"

"I know, but Merope was there, too. I saw her. And she hasn't gone yet. She went there-will go there after Mike saved Hardy and we did all the other things, so they can't have affected the outcome of the war."

But Mr. Dunworthy was shaking his head. "At the point when you saw her, there would still have been a VE-Day to which she could go. The course of history-past and present-would have remained as it had always been until the alterations reached a tipping point. That is why we are able to be here, even though we're part of that unaltered future. And why Eileen could have gone to VE-Day. It would have remained unaltered until the moment the final alteration occurred and the continuum could not correct for it-"

"And then everything would change."

"Yes."

"But you said ..." She frowned, trying to grasp it. "I don't understand. Hadn't that tipping point already happened? The drops had stopped working."

"Not entirely. Mine was still working in mid-December."

"So the tipping point happened between our finding Merope and mid-December?"

"No, it may have been after that. I don't know when exactly. I wasn't able to get to my drop till the night after I saw you all on the steps of St. Paul's."

It was something one of us did the night of the twenty-ninth, Polly thought. They had delayed the air-raid warden on the steps of St. Paul's so that he hadn't been in time to save someone. Or Theodore's screaming departure had delayed the pantomime a crucial few minutes so that one of the audience hadn't made it home to their Anderson in time. Or her presence on the roofs had altered the actions of the fire watch in some way that would prove fateful later on.

Or it might even have been Eileen's taking the bombing victims to hospital or Mike's saving the firemen. In a chaotic system, positive actions could cause negative outcomes. Like losing the war.

Winning it had always been a near thing. "We are hanging on by our eyelids," Churchill's chief of staff had said. Events had been balanced on a knife's edge, and they had tipped the balance, and the Germans had won the war.

Oh, God, she thought, Hitler will execute Churchill and the King and Queen and Sir Godfrey, and send Sarah Steinberg and Leonard and Virginia Woolf off to die at Auschwitz, and Mr. Dorming and Mr. Humphreys and Eileen's vicar off to die at the Russian front. He will breed the blondes, like Marjorie and Mrs. Brightford and her daughter Bess, to blue-eyed Aryans, and starve Theodore's mother and Lila and Miss Laburnum. And turn Theodore and Trot into young Nazis.

But not Alf and Binnie, she thought. Or Colin, no matter what sort of world he's born into. They'll never go along with it.

Hitler would have to kill them first. And he would.

"Oh, God," Polly murmured. "Mike was right. We lost the war. We ruined everything."

"No," Mr. Dunworthy said. "I did."

I have got to know the worst, and to face it.

-SIR J. M. BARRIE, THE ADMIRABLE CRICHTON London-Winter 1941 "WHAT DO YOU MEAN, YOU DID IT?" POLLY SAID, STARING at Mr. Dunworthy sitting there by the pub's fire with her coat over his knees. He had stopped shivering, but he still looked chilled to the bone. "You can't have lost the war. How? By coming to fetch me? Or something you did since you've been here?"

"No," he said. "I did it before you and Michael and Merope were even born. When I was seventeen years old."

"But-"

"It was the third drop we'd done to World War Two and the first to the Blitz. We were still refining the net coordinates, and all I had to do was to verify my temporal-spatial location and go back. I'd come through in the emergency staircase of a tube station, and when I found out I'd come through to the seventeenth of September 1940 instead of the sixteenth, I was frightened I might be in Marble Arch." He stopped and stared bleakly into the fire. "Perhaps it would have been better if I had been."

"Which station were you in?" Polly asked.

"St. Paul's," he said. "And when I found that out, I thought taking a side trip to see the cathedral couldn't hurt." He smiled bitterly. "I'd been fascinated by it since I first saw the fire watch stone as a boy. And here St. Paul's still existed. So I ran up the street to look at it, just for a moment."

He put his hands to his head. "I wasn't looking where I was going-an apt metaphor for the entire history of time travel. I collided with a young woman, a Wren, and knocked her bag off her shoulder, and all of her belongings spilled out and onto the pavement." He stared blindly ahead as if he was seeing it happen. "Coins scattered everywhere, and her lipstick rolled into the gutter. She was carrying several parcels, and those flew out of her hands as well. Two other people-a naval officer and a man in a black suit-stopped to help, but it still took several minutes to gather everything up."

"And then what?" Polly asked.

"And then the sirens went, and the Wren and the two men hurried off, and I went back to St. Paul's Station to my drop and to Oxford."

"And?"

"And a Wren was killed in Ave Maria Lane that night."

"And it was the Wren you collided with?"

"I don't know. I never knew her name. I don't even know if she was the one I affected. It might have been the black-suited man. There's no record of a naval officer being killed that night, so I don't think it was him, though my delaying him might have set in motion a sequence of events which killed him the following day, or the following week."

"But you don't know for certain that you killed any of them, or that the collision altered anything at all."

"That's true. It may not have been the collision. I gave two children a shilling to tell me the name of the tube station, and had a conversation with a station guard. And I interacted with a number of other people in the station, pushing past them or making them go round me. I might have delayed any of them a critical few moments, and the difference might not have resulted in anything till much later on."

Mike had said the same thing about the Dunkirk men he'd saved-that the alteration might be invisible for months, even years.