The police doubt the credibility of the evidence against Torben Witt and continue to watch over the Claassen residence. Meanwhile, Ina Grote helps with the arrest of Onno Wulf.

It seems as if Torben has been caught red-handed and the evidence adds up against Onno. Can they convince the police of their innocence?

Harry and Henning have to apologize to Ina Grote and Onno Wulf. Meanwhile, the truth about what happened at Frauke Claassen's house is revealed.

After it is revealed that Frauke Claassen tried to frame Torben Witt, Eileen Claassen asserts her independence. Harry and Lothar get revenge on Dirk for his role in the confusion surrounding Harry's training program.

Everyone at the station speculates wildly when Dirk is mysteriously called away. Meanwhile, Katja observes the anniversary of her father's death.

Lothar finds out why Nicki is so stressed out about her upcoming exam. Meanwhile, Katja and Ben investigate when someone overhears a gunshot.

Katja learns that the gun found on a teenager is the weapon used years ago to kill her father, who was also a cop.

While Katja, Ben, Henning, and Harry all look into the weapon that has surfaced, Lothar meets Nicki's father, who is a very difficult person.

Katja tells her mom that the police have found the murder weapon that killed Katja's father. Meanwhile, the wife of the top suspect is brought in for questioning.

Everyone weighs their options regarding the suspect's wife, who remains in custody, while Nicki's father proves himself to be a very difficult person to get along with.

Frau Starke finds a diary that reveals that her husband had an alibi, proving he couldn't have murdered Katja's father.

Joe tells Katja that her father actually committed suicide. The others back at the station are unable to find out any information about what happened to the weapon that night.

While Katja deals with the terrible news about her father's death, Lothar argues with Joe about how the situation was handled.

As they consider destroying the murder weapon, Lothar, Ben, and Katja go back to the scene of Katja's father's death.

When the autopsy records reveal that Katja's father couldn't have killed himself, the group realizes it is time to go after the murderer. Meanwhile, Nicki learns that her father is deceiving her.