Sázka na třináctku May 26, 1978

A mail truck is robbed near the small town of Kostelec, during which the perpetrators steal CZK 2.5 million. The local police fail to solve the case. After some time, a young and capable lieutenant Charvát arrives from the Prague CID. While he is getting acquainted with the circumstances of the case and the evidence found, he makes friends with the handsome Květa, the daughter of the hostel manager Weisse. The complicated relationship that develops between the two lovers is in no way comparable to the complexity of the criminal case that brought Charvat to Kostelec. Things get even more complicated when someone murders Malásek, a local brawler and drunkard, with a shotgun. He is actually Květa's husband. And his death, according to Charvat, is connected to the mail robbery...