When a major drugs dealer seeks vengeance for the death of his family, policemen Harpur and Iles must do all they can to prevent a bloodbath. Following the murder of his wife and son, tycoon drugs dealer Mansel Shale is determined to get vengeance - and he wants another drugs baron, Ralph Ember, to help him. Having heard of the movie Strangers on a Train, in which two men agree to undertake each other's murders as a way of preventing detection, Shale suggests he and Ralph should have a similar arrangement - and Ralph is in no position to refuse. When he learns of the plan, Assistant Chief Constable Desmond Iles fears that if things go wrong, the hard-won peace he and Harpur have established in the city will be seriously threatened. The two top policemen find they have their work cut out to limit the damage and restore tranquillity.