When Gardiner organises a British tour for a South American dance company and discovers a plot to discredit their patron, he intervenes on the British Government. But South, a hired killer, stalks his every move.

When Professor Preece is sent to prison for passing secrets to a foreign agent but escapes to settle accounts with the real traitor (his son), a chance meeting with Judy alerts Gardiner to Preece's plans.

Before Gardiner can arrive at a sleazy hotel to keep a rendezvous with a man claiming to have important news, South kills the informer. Gardiner discovers the man's body and a reel of film - which sets him on the trail of a powerful adversary.

A young boy 'adopts' Judy and declares that he will stay with the Gardiners, and then produces a £100 note to pay rent. This odd event leads Steve to uncover an uncover an assassination plot against a French politician, whom South has been hired to kill.

When Judy has a nightmare during which she is murdered by a mute killer and then meets South, the man from her dreams, in a train corridor, Steve finds far more than he bargained for on his return home.

Gardiner is approached by a young girl who asks him to sign a petition on behalf of South, who is applying for a reprieve. They argue and the incident places both in danger when Gardiner is mistaken for an American journalist.

The body of an actor, covered with flowers and found in a car, leads Gardiner to bait a trap for South.