Apparently the Gutenberg Project has a lot of H.Beam Piper on line free.
""Crossroads—of—Destiny!" he intoned, and hit the edge of the tray again, Bong! "This is the year 1959—but not the 1959 of our world, for we are in a world of alternate probability, in another dimension of time; a world parallel to and coexistent with but separate from our own, in which history has been completely altered by a single momentous event." He shifted back to his normal voice.
"Not bad; only twenty-five seconds," the plump man said, looking up from his wrist watch. "And a trained announcer could maybe shave five seconds off that. Yes, something like that, and at the end we'll have another thirty seconds, and we can do without the guest."
The above quote comes from his story "Crossroads of Destiny". I read it and immediately thought of the opening of "The Twilight Zone".
