Prof. Erling and his financial backer Victor build a prototype time machine to snatch objects from the past. Latest find, a statuette, radiometrically dates to 5200 AD! When this draws colleague Richard Hedges to the island lab, Erling reveals that 20th-century objects put in the machine seem to be "traded" for analogous future objects by intelligent life. And on the sly, Victor's been trying to get a living visitor. Does the future need help, or is the present in danger?

A young man steals a car and ends up involved in a pedestrian fatality. The only witness is a girl he has just met. He threatens her life if she talks, so when she refuses to tell what she knows, she is sent to reform school.

Aliens equipped with venomous claws invade a small town, but the town's teenage population is mobilized to fight the menace.