A fisherman who knows more than he's telling; men with binoculars and a fast American car; and waiting out at sea a man with a high-powered rifle...

John's father has disappeared and the police don't seem interested. John and Susan decide to solve the mystery for themselves, but they don't know someone is watching them, all the time...

John catches sight of his father again, with three other men: he also sees the police in pursuit. The chase is on!..