Yugoslavia before Marshal Tito's break with Russia. In a cafe facing the harbour of Dubrovnik two Englishmen are sitting, watched by Zarko, the Chief of Police. Robert Hudson, an engineer, has known John Raikes for only three weeks-Raikes has been introduced to him as a technical consultant from the British Board of Trade, and the two of them are completing negotiations for the supply of certain machinery to the Yugoslav Government. Within a few hours Raikes is reported dead-"a tragic accident while bathing," says Zarko. Hudson, alone in an atmosphere of ill-concealed hostility, determines to fulfil a mission of which he himself has only a hazy knowledge.