A serial killer is roaming international and hence anarchic space looking for victims to kill with impunity. He finds his way to a self-sufficient spaceship owned by a scientist who allows him to dock and rest. The scientist explains that he is studying vampire humans who he has discovered and kidnapped. He is trying to figure out how they derive their powers and if he can genetically modify humans to have the benefits of vampirism without the downsides.
The serial killer is fascinated and decides to spare the scientist. The serial killer goes to sleep, and wakes up in his room to find he has been strapped down. The scientist aims to enhance him genetically using elements of the vampire DNA. The scientist performs a procedure on him. The scientist also removes genes associated with psychopathy from the serial killer.
When the scientist finishes the procedure, the serial killer is a superhuman without the urge to kill anymore. He feels terribly guilty over what he has done and explains to the scientist his past. The scientist suggests he be a force for good now, and the man agrees. With that he programs the ship’s navigation to burn up all the fuel and launch the ship on a trajectory away from humanity, so the scientist and the vampires can never bother mankind, while he himself takes an escape pod and pilots back towards civilization.
His pod is picked up by a large spaceship used by a touring rock star in this part of space. The ex-serial killer then becomes a roadie for the rock star to make money to pay for his education, studying science, biology and engineering so he can benefit humanity as much as possible for as long as possible. He does this as penance for the people he murdered.