Australian detective Scobie Malone (Rod Taylor) is sent to London to arrest and return for trial the Australian High Commissioner to the UK, Sir James Quentin (Christopher Plummer) in this 1960s Cold war drama. Malone's boss believes there is sufficient evidence to charge Quentin with the murder of his first wife that occurred many years earlier. On Malone's arrival in London he finds that Quentin is chairman of an international conference attempting to bridge political divides through trade. Malone agrees to allow Quentin to conclude the conference but stumbles into a plot to assassinate the High Commissioner. Instead of arresting Quentin, Malone becomes his bodyguard and foils an assassination attempt at the Wimbledon Tennis Championships. Plots and counter plots abound but Malone must track down the real killer of Quentin's first wife and keep him alive long enough to prove his innocence!!