Clarification:- This is a plot summary for the English language version of Circus of Fear / Psycho-Circus only. The German language version may have a different ending.In London a gang of criminals carry out a daring, armed robbery of an armoured car - during which one of the security guards is shot dead. Scotland Yard assign Police Inspector Jim Elliott (Leo Genn) to the case but there initially seem to be few leads. However, just when the trail seems to have gone cold a curious potential lead comes to Elliott's attention from a rural area of southern England. Some of the stolen bank notes from the robbery seem to have turned up at businesses in the vicinity of the winter quarters of Barberini's travelling circus - which Elliott remembers were performing in London at the time of the robbery.Elliott initially goes undercover as a photographer to visit the circus and speak to owner Barberini (Anthony Newlands) but soon has to dispense with his cover when the body of one of the armoured car robbers turns up inside a sack at the circus. The robber has been murdered with a throwing knife with a diamond-shaped design on the handle. Elliott begins to find out that the circus is riddled with petty rivalries and some darker secrets. A short time after circus starlet Gina (Margaret Lee) is also killed.Elliott identifies a number of potential suspects - Gregor (Christopher Lee), the circus lion tamer, who wears a black mask to conceal his mutilated face. Mario (Maurice Kaufmann), the knife-thrower, who was insanely jealous of Gina's suitors. Carl (Heinz Drache), the circus ringmaster, who believes that his father was killed by Gregor's twin brother. Mr Big (Skip Martin), a dwarf circus clown, who it is discovered has been blackmailing Gregor. Eddie (Eddie Arent), the circus' bookkeeper, who has never been allowed to realise his life-long ambition of being a circus performer. Natasha (Suzy Kendall), Gregor's niece, the daughter of the man Carl thinks is responsible for his father's death.Elliott eventually establishes that Gregor found the missing money from the robbery and hid it beneath one of the lion cages in an old suitcase. Gregor tries to escape with the money but is murdered by a masked figure. Following Gregor's death it is discovered, when his mask is removed, that he has an un-mutilated face and is in fact Natasha's father. It is then also revealed that Carl's father died in an accidental fall. Elliott is convinced that although Gregor had the stolen money he was not responsible for the two murders and that the murderer is still at large. Acting on a hunch, he arranges for Barberini to finally give Eddie a chance to assist Mario in his knife-throwing act. When Mario switches weapons and uses the knives identical to those used in the murders, Eddie breaks down and admits that his envy of the circus performers drove him to commit the murders.