In this classic novel by the Science Fiction Grand Master, a writer searching for explanations uncovers the existence of mutants and multiple Earths: "First-rate Simak" (The New York Times).

Author Jay Vickers would like nothing more than to be left alone so he can finish his next book. But "there's something strange going on," as his peculiar neighbor, Horton Flanders, says. The market is filling with new inventions that supposedly last forever—cars, razors, cigarette lighters, and more. Individuals and whole families are disappearing. Soon, even Mr. Flanders vanishes—but not before leaving Vickers a note.

Following Flanders's advice, Vickers travels to his childhood home, where he makes a fantastic discovery. It is a mere child's toy, a brightly colored whistling top. But for Jay, it leads to other worlds and answers all his questions. What happened to all the vanished people? Who is behind these helpful inventions? And what sort of being would want to stop them?

"Unforgettable." —New York Herald Tribune

"Solid entertainment, with plenty of startling plot twists." —The Magazine of Fantasy & Science Fiction

"Some of the most ingenious plot twists in recent science-fiction." —Galaxy