Henry Harrison is twelve-years-old and something of a minor tearaway. He is also, quite incorrectly, the prime suspect of the armed robbery of a market trader and, as the novel begins, on the run from the law.

Anxious to clear his name, he finds midnight sanctuary, illegally, in the home of a retired professor of physics, but rather than immediately hand him over to the police, the professor listens to his trespasser's tale with some sympathy and even offers to help Henry clear his name. This he does by allowing him to use his newest, most secret and prized invention - the ability to travel in time.

What follows is a suspense filled journey through time and space as when the kindly professor is kidnapped by terrorists Henry joins forces with the old man's grandson in a desperate bid to rescue him.