When an armoured car is robbed, in a daring daylight raid on Tower Bridge, one of the gang hides the money in Barberini's Circus. The police also investigate people being murdered by throwing knives. Gregor (Christopher Lee), is a facially scarred lion tamer, one of the many suspects in the case investigated by Scotland Yard's detective Elliot (Leo Genn). His examination of all the clues leads to a final denouement in front of the assembled suspects during a knife-throwing act.