Shots are fired in a police chase f ollowing a bombing in the heart of Vienna, and the owner and trainer of the police dog, Rex, is killed. Inspector Moser saves Rex and decides on the spur of the moment to take him into his car - much to the dismay of his colleagues. Rex repays Moser by accompanying him on his investigations and proves himself an invaluable partner in Moser's fight against crime...

When Hans Felsner, owner of a resturant has an apparent heart attack, it is soon discovered that it was actually a murder. Moser is called in and then Hans Felsner's sister-in-law also turns up dead.

A particularly horrendous case of organ trafficking is believed to be the motive for a series of murders.

One by one, ladies living alone in the center of Vienna disappear. Moser suspects violent crime, but so far no bodies have been found...

A prisoner makes a violent escape. His accomplice is wounded and left behind. Fleeing from the police, the escaped prisoner holds a ballerina class hostage and demands the release of his friend.

A woman is found dead in the park surrounding the Schönbrunn Palace. Moser is not convinced the man they suspect is the one they are looking for...

In the psychiatric clinic at the "Steinhof", a spacious Art Nouveau complex, mysterious deaths occur among the patients. The clinic pathologist confidently turns to his colleague Dr. Graf and asks him for help. All patients died in the same way: they drowned in a bathtub. Graf informs Moser, who wants to take up the investigation. But the prison management refuses a police investigation. Moser decides to be admitted to the institution as an "alcoholic". He entrusts Rex to his assistant Stockinger. But before he knows it, Rex flees and hides on the hospital grounds. As a result, he gets Moser into big trouble, because where should he hide Rex? Meanwhile, the situation escalates dramatically, Prohaska, the ward nurse, wants to eliminate Moser. With a daring jump through a closed window, Rex saves his master's life...

On New Year's morning, a woman is found hanged in the attic of a middle-class terraced house. No suicide, as it turns out: The box on which the dead woman allegedly stood is too small. During the interrogations, the residents of the house make every effort to present themselves as "fine people". But the ideal world is only faked: Rex finds a bound and gagged man locked in a refrigerator in the attic. He is a homeless man who was beaten down by two residents in search of his friend. The wanted man is found dead shortly afterwards. What actually happened on New Year's Eve in the "fine house"?

Stefan Lanz, a successful young stockbroker, is a member of a yuppie clique that meets regularly at a castle near Vienna for group sex weekends. When Lanz is taken for the second time in the hospital shortly before a harmless knee operation, he becomes suspicious. He gains access to his medical record and discovers to his horror that the word "positive" is entered under the heading HIV. Lanz concludes that someone from his clique has infected him. He decides to take revenge on each one and escapes from the hospital. Shortly thereafter, Commissioner Moser has to deal with two murders that seem to have nothing to do with each other. But then it becomes apparent that they were committed with the same murder weapon. He finds out that the victims must have known each other, because both knew a man: Stefan Lanz...

In a bush of the Praterauen you can find the body of a 12-year-old girl who had not come home after attending a piano matinee. A little later, little Christl Strobl, who had just won a prize at a piano competition, disappears. Moser and Stockinger find out that both girls had the same piano teacher. It turns out that the piano teacher Hoffmann has no alibi. When the two find Christl's body in the multi-storey basement of his house, the case seems solved: Hoffmann is arrested. To Moser's surprise, however, he suddenly presents an alibi. The search for the real culprit leads back into the underground cellars of Hoffmann's house...

A bomb hidden in a teddy bear explodes in the window of a toy store – the second attack within a short time. Both times they were teddy bears from the Neuwirth company. Commissioner Moser, who is handicapped by a leg in plaster, suspects that these attacks are intended to damage the company. From the young, attractive boss Diana Neuwirth he learns that there are many people with revenge motives: After the death of her father, Diana had to dismiss some employees. The mechanic Gerhard Böck, who had lost his right hand in a factory accident, and Paul Steger, with whom Diana had an affair and by whom she now feels threatened, come under suspicion. When Paul Steger is found dejected in the factory, the case takes a surprising turn. On the hunt for the perpetrator, Richie Moser and Rex are in mortal danger: A third bomb threatens to blow up...

The stonemason Franz Nemec, together with his accomplice Gruber, works as grave robbers at the Vienna Central Cemetery. He receives the order from the antique dealer Kronhauser to get Beethoven's head out of his crypt. Nemec carries out the order and is found beaten to death a short time later. Inspector Moser takes over the case and discovers how Nemec made his money. In order to get to the perpetrators, Moser lets it be known in the press that Beethoven's head has long since crumbled to dust. His trick seems to work: Kronhauser's client, a certain Strasser, demands his money back from the antique dealer. He suspects that Kronhauser cheated on him and sold him a false head...

In Vienna's sewage system, workers discover a washed-up sports bag with body parts. Moser finds out at which point in Vienna's gigantic sewer network the bag must have ended up in the wastewater. A little later, a witness comes forward who has observed the exit of a man from an advertising pillar, through which one can descend into the canal system. Rex shows Moser the exact location of the body. A little later, a second bag is found, this time with the body of the body. Dr. Graf discovers a tattoo on his body that allows conclusions to be drawn about the identity of the stranger: Josef Hartmann, who was in prison for bank robbery. Moser suspects that Hartmann was involved in a bank robbery that had taken place shortly before. In order to confirm his suspicions, the cashier Erika Reichel is questioned again. The case takes a surprising turn when Mrs. Reichel confesses that her boyfriend and Hartmann knew each other...

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...