The alleged murderer of a policewoman, Frank Keller, applies for release from preventive detention after 15 years in prison. However, it is rejected. Out of desperation, Keller takes his lawyer hostage and flees the courtroom. His first destination is the house of the edgy and highly respected police instructor Bruno Theweleit. Keller is said to have shot his colleague 15 years ago. After the incident, young policewoman Lena Frey sets off on her own search for clues and comes across more and more contradictions in the version of events that is supposed to have happened 15 years ago. This draws the displeasure of Theweleit and the shady inspector Günther Lehmann, who was also involved in the incident. After a meeting with Keller, Frey begins to doubt the man's guilt.