When a blood-soaked teenage-sized hoodie is found in a used clothing collection, Ellen Berlinger and her colleague Martin Rascher are alarmed. For Martin, the find is a bad signal. For years, an unsolved series of murders of young people has weighed heavily on his soul. Now he's convinced another teenager has been killed. In Ellen's eyes, that's just one of the possible explanations. But she's worried too. Because the sweater could belong to Jonas (Luis August Kurecki), the son of her cousin Maja (Jule Böwe). Ellen has been transferred to Mainz because Maja is helping her look after her little daughter Greta (Suzan Majewska). The inspector has developed a special bond with the closed Jonas.
The 13-year-old was supposed to be on a trip with friends after the school festival the night before, but Ellen can't reach him there. Jonas' parents aren't worried yet - unlike those of 16-year-old Marie Blixen (Aniya Wendel). Marie was also at the school festival, but never returned from there. The wealthy parents fear a kidnapping in order to extort ransom money from them. The hoodie, on the other hand, they say, isn't Marie's. But who can say for sure with the widespread gray sweaters? The interrogations of Marie's classmates about the evening of the school festival don't yield much, not even Max (Paul Michael Stiehler), with whom Marie flirted, has anything to say. Then a ransom demand actually comes in.
An attempt is made to hand over the money - but Marie is already dead, beaten and left on a deserted site. There are traces of the hoodie on the body. Ellen begins to fear Jonas is involved.