Ko zaradi nasilne smrti umre še tretja članica šolskega kolektiva, kriminalisti posumijo, da se je na šoli pojavil serijski morilec. Inšpektor Vrenko je prepričan, da se storilec skriva v kolektivu, katerega člani pa si njegovo ekipo podajajo kot namiznoteniško žogico. Zdi se, da se preiskava vrti v začaranem krogu. Pa vendar, preskok v razmišljanju inšpektorja Vrenka pripelje do morilca, ki se je od vseh sodelavcev v kolektivu zdel še najmanj škodljiv.
When a third member of the school staff dies as a result of a violent death, criminal investigators suspect that a serial killer has appeared at the school. Inspector Vrenk is convinced that the perpetrator is hiding in the team, whose members pass his team like a table tennis ball. The investigation seems to be spinning in a vicious circle. However, a leap in Inspector Vrenk's thinking leads to the killer, who seemed the least harmful of all the co-workers in the collective.
