Commissioner Max Steiner and his police dog Rex are on a case involving explosives. In a restaurant on Stephansplatz, a customer, Sascha Trautmann, is sitting on a bomb. If he moves or stands up, the restaurant will explode. Barely saved, the man disappears into the night. The next day, he dies under mysterious circumstances while riding in a horse-drawn carriage. A false identity card suggests the deceased might have been a spy. Only the first name of the woman with whom he had his last date is known. Max and his colleague Felix Burger, accompanied by Rex, begin their investigation.

A dead baker, many suspects: Rex searches for the truth in a village full of mysterious motives. In the bakery, baker Hans Schlager is discovered dead in the oven by his son early one morning. It quickly becomes clear that the argumentative baker had numerous enemies. Several neighbors come under suspicion, including a bookseller and a pharmacist. While Max and Felix question the suspects, Inspector Rex uncovers crucial clues and sheds light on the puzzling murder case.