Ace and the Seventh Doctor walk along the side of the Red River to a crime scene. There they meet reporter Walter Orpheus. The Doctor introduces himself as the Professor and is taken for an official person by the police who invite him to examine the evidence.
The Doctor hands Ace a newspaper clipping detailing a series of attacks on the bank of the river. This crime scene is that of the latest victim - a teenage girl, who has survived the attack, like every victim before her, and is in hospital. The attacker has been labelled as "the Ripper", but the Doctor suggests that the attacker may be an animal, judging by the wounds.
At St Saviour's Hospital, the Doctor goes through the case histories of the victims with Doctor Leonard Milroy and they discover that all have had an organ removed, but have never had the appropriate surgery. All the victims had medical issues that stemmed from the lost organ prior to their loss.
The Doctor and Ace spend the night at the university, where they sleep in student halls. The next day they are informed that the Ripper has been caught. There has been another attack, a man has suffered wounds to the thorax and was suffering from chest problems. Ace and the Doctor realise that the attacker is performing surgery on people, a misunderstanding having developed.
Stan Gorman, whose brother was a victim, has the Ripper cornered in a tunnel and is preparing explosives to kill him. The Doctor, Ace and Milroy enter the pipe. As a precaution, the Doctor has Ace cut the wire. Suddenly, a silver ship passes them and flies off into sky. The Doctor laments the loss of "our friend" and Milroy is left hoping for his return.
- Elsa Havenhand is one of the Ripper's victims. She suffered from hypersplenism.
- Stan Gorman owns a company called Gorman Construction.
- Unlike the other stories including the reader's character, here Sophie Aldred narrates Ace in first person.
- The story's title is taken from a newspaper headline in a clipping the Doctor hands Ace.
to be added