Collects 23 stories: The Red Brain; The Holiday Act; Something from Above; Raiders of the Universes; A Race Through Time; Farewell to Earth; Colossus Eternal; The Atom Smasher; The Blinding Shadows; Life Current; The Whisperers; Murray's Light; Earth Minus; Finality Unlimited; Infinity Zero; Black Fog; The Crystal Bullet; On the Threshold of Eternity; A Trip to Infinity; Requiem for Mankind; and the title story plus 2 previously unpublished stories: "A Stranger Passes" and "If".