When the owner of two vegetable shops at the Naschmarkt is shot, the investigation is obstructed by the market people. Shortly afterwards, a truck driver is killed in the same market: The dead man, Werner Gredl, is the husband of the Russian landlady Irina. Inspector Moser disguises himself as an unskilled worker and investigates undercover at the vegetable market. He realizes that Irina is afraid: she is being blackmailed. In his undercover investigations, Moser tracks down a dubious group. The encounter with the people becomes life-threatening for him and Irina. Only Rex can prevent disaster...