After a UFO sighting, a mysterious phantom in a bizarre outfit starts attacking people in San Fernando Valley.

Lt. Col. Glenn Manning is inadvertently exposed to a plutonium bomb blast and although he sustains burns over 90% of his body, he survives. Then he begins to grow, but as he grows he starts losing his mind. By the time he stops he is 50 ft tall, insane and is on the rampage.

Joyce and Fred MacNeil's honeymoon comes to an abrupt and unsatisfying halt when Fred is accused of murder. Railroaded into prison through the efforts of politically ambitious assistant DA Marlin, Fred awaits his doom on Death Row, while Joyce works overtime on the outside to clear her husband's name

Paul Kriza is a cashier of a bank in a small town, and the happy husband of Anna and the father of four children. He is sent to New York to deliver some securities for the bank. There, he is tagged as easy-pickings by a con-game gang and Mary Brown, gang accomplice, proves he is. Waking up in the morning he discovers he has been robbed of the securities and, when he confronts the gang, he is hit on the head and taken out to be left on a railroad track. He comes to, struggles with the henchman and the man is killed when a train comes roaring by. Paul escapes but his watch is found and he is reported as the dead man. But he can't go home again.

An attractive reporter investigating the mysterious destruction of an Illinois town stumbles upon a secret government laboratory conducting radiation experiments on vegetables. The lead scientist is eager to help find out what happened. Together they discover that giant grasshoppers are behind the devastation. Worse yet, thousands of them are headed toward Chicago! Can they be stopped... or is this the BEGINNING OF THE END?

Atomic scientist/pilot Doug Martin is missing after his plane crashes on an reconnaissance mission after a nuclear test. Miraculously appearing unhurt at the base later, he is given sodium amethol, but authorities are skeptical of his story that he was captured by aliens determined to conquer the Earth with giant monsters and insects. Martin vows to use existing technology to destroy them.