When the industrialist Erich Staller is kidnapped, the police initially learn nothing despite ransom demands in the millions, because the perpetrators threaten to kill their victim. Shortly thereafter, the body of pensioner Franz Pichler is discovered in an empty railway carriage. Richie Moser and his team find the clue to the crime scene: a garden house on the outskirts of the city – prepared as a prison. Meanwhile, Staller tries to provoke his kidnappers so that he can identify them. During a routine interrogation in connection with the pensioner murder, Moser meets Heidi Staller, the wife of the kidnapped, but she refuses to cooperate. During their surveillance, Rex intervenes and the kidnapped provides a life-threatening surprise...