In Vienna, two nightclub owners have been murdered within a short time. Commissioner Moser is hot on the heels of the alleged perpetrator, the professional killer Oleg Karenin. He witnesses a telephone conversation between Karenin and his client Matzner. What he overhears is enough to arrest the killer. But Matzner does not give up and has Rex kidnapped. He demands of Moser: Either he retracts his statement and Karenin is released, or Rex must die. Moser puts all his eggs in one basket: he retracts his statement and tries to find Rex before Karenin can leave the country. The only clue to his partner's whereabouts is the sound of a landing plane, which could be heard in the background when the blackmailers called...