In Joe's mechanic Schrotti's Bauwagen is found pest controller Leo Bonacker, who was fighting a mice infestation. His gas-mask was filled with toxic manioc. His ex-spouse and business partner, who last nearly all clients, had access and admits having stolen 60 000 Euro but also puts the team on the trail city supervisor Till Prechtel's crooked deals with Leo, notably blackmailing chefs like Jonas Bömmle, which both deny. * Bömmle's anti-consumerist Petra Meiser, to puzzled Rico's taste, filed a complaint for her ferret's death in a cockroach trap placed in the restaurant, but that seems too measly as murder motive, if the only one. Just after Jo learns his mechanic mate was tricked earlier by Till Prechtel, the corrupt crook suffers the toxic poisoning in his own car. Rico ties it all together after finding the missing link, brilliantly but bitterly.