Mysteries of Unexplored Worlds #10 (1958)

In a top-secret laboratory, a seemingly ordinary assistant named Moseby secretly replaces the real Moseby and plans to steal classified data on a mysterious, powerful new element. After tampering with the security system and narrowly avoiding exposure, he panics upon realizing the element’s radiation may have already altered him—only to discover his own reflection has changed in a horrifying way.

On a distant, uncharted planet, two explorers debate whether to venture outside their ship, uneasy about the strange, silent world they've landed upon. As one hesitates, a sudden, unsettling presence draws their attention—then a child's voice breaks the tension, playfully noting a dusty drawer and a fleeting glimpse of something silver, leaving the fate of their mission uncertain.

Clyde Sommers, a petty thief, steals a mysterious crystal egg from a pawn shop, only to discover it contains a key that can open any lock—doors, drawers, even a safe. As he revels in his newfound power, he’s confronted by the pawnbroker, who claims the key was never meant for theft, and warns him of its true purpose. When the pawnbroker vanishes and Clyde finds himself trapped in a web of questions, he’s left wondering who the man really was—and what the key was truly meant to unlock.

Jo, a young man reeling from a terminal diagnosis, stumbles into a strange, autumnal street where he encounters a woman who greets him as her husband and children call him "Daddy"—a vision so vivid it feels like a glimpse of a life he never had. Disoriented and shaken, he awakens to find the moment gone, leaving him to wonder if he truly glimpsed a possible future, or if the illness has twisted his mind.

In "Saucer-itis," a man's strange behavior—muttering about flying saucers and acting oddly—has everyone convinced he's insane. But as his antics grow more elaborate, it becomes clear he's not just eccentric—he's hiding something far stranger than anyone imagined.

In "The Strange One," a lone man washes ashore on an isolated island only to stumble upon the ruins of a forgotten futuristic city. As he flees from unseen voices echoing through the silent streets, he realizes too late that the city’s inhabitants are not gone—they’re simply invisible.