Robert Maitland, a 35 year-old architect, is driving home from his central London office when his car has a blowout, it swerves and crashes into a traffic island lying below three converging motorways. Uninjured, Maitland climbs up the embankment to flag down a car. But he soon finds out that no-one in the rush-hour traffic will stop for him, and he is trapped on the island, where he remains.