Police officers Nils, Melanie, Boje and Franzi from Precinct 21 are involved in a spectacular chase as they pursue the car thief Dennis Baumeister. But was he actually trying to do more than steal a car? This question arises when they find four-year-old Finn Greve on the back seat of the vehicle. His parents, Jan and Katja Greve, claim to have no idea why anybody would want to kidnap their child. But now Nils and Melanie discover that Baumeister works as an "enforcer" for a notorious loan-shark, and gradually the truth emerges: Jan Greve is addicted to gambling and has run up immense debts. The whole thing was planned to pressurize him into repaying the money he owes. But by the time Nils and Melanie get hold of the loan-shark, it's almost too late...
Boje and Franzi have become involved in an absurd argument between neighbours. Veronika Waldmeyer accuses the woman next door, Elke Schmitt, of having deliberately run over her beloved cat. Boje and Franzi manage to smooth things over, but soon afterwards they are called back - because Frau Waldmeyer has attacked and injured Frau Schmitt with a gardening tool. Boje and Franzi have no alternative but to take the furious Frau Waldmeyer down to the police station, where the case takes an unexpected turn.
Franzi hasn’t been a police officer for long, and now she gets first-hand experience of just how challenging her profession can be: she is attacked while on duty and narrowly escapes with her life. Her superior officer, Berger, decides she should therefore be taken off active duty.
Nils and his girlfriend Anna, a doctor, are so much in love that they are thinking of moving in together. Melanie keeps on making critical remarks about the whole situation, apparently jealous of her colleague’s happiness. And Anna’s 10-year-old son Ole also seems deeply disturbed by the relationship between his mother and Nils.