I nodded.
"In the first time-line," Golfin said, "the one I started out to investigate, you were actually killed. I know now how it happened. You see, Sarah Fish is a blackmailer. George Wile was one of her victims. To get out of her clutches he had planned on killing her. It was a perfect setup for him. Several of her blackmail victims were there. All he had to do was stick her with the poisoned needle and sit back. Nothing could be pinned on him. Motive? A dozen of those present had equal motives.
"But you were there. A pickpocket. You lifted his wallet. He wouldn't have felt your light touch ordinarily, but he was acutely conscious of those spare poisoned needles. He had one in his fingers. Within a few moments Sarah would have been killed. You changed things. He killed you instead, and in the excitement stole back his wallet. And of course he didn't go through with his original plan to kill Sarah Fish. And also of course, the police never solved your murder. That's why I chose it in my first attempt to change the past. It was an ideal mystery. I could solve it and at the same time save your life.
"I went into the past and watched your every move. But George Wile was too smart. Even watching I couldn't find out who had done it. So I went back into the past again and began my great experiment, an attempt to alter what has already happened.
"I succeeded—but not the way I had hoped. There is an inertia to events. That inertia in events made you steal his wallet the second time—and plant your own on him. You left before he discovered the switch. He came after you to kill you here. It was then you gave me the identity of your killer. After that I went back to my original point again. At the proper time I did what you had done. I picked George Wile's pocket. He felt me do it. Again—the inertia of events—he tried to stick me with the poisoned needle. But I was ready for him. I deflected his hand and shoved. He stuck himself."
Golfin grinned. "Sure I planted your wallet on him. But who can say whether it was my own free will or the inertia of events that made me do it? The morning papers will carry the story exactly the same as it was in the first time-line. A tremendous inertia of a single event."
"But what about me?" I said wildly. "The police will check. They'll know he isn't me."
Golfin shrugged. "I doubt it," he said. "My guess is that Sarah will identify him as you and keep quiet. To protect her racket, George will be buried as Ben Smith. George Wile's relatives will report him missing. He'll never be found. 'Your' murder will remain unsolved."
"I'm getting out anyway," I said. "I don't want to chance it."