Carnal Desire

S4, E1: In a forest parking lot, Hubert and Staller discover a refrigerated truck belonging to the Semmling wholesale butcher shop. Strangely enough, the truck seems to have been there for some time. And indeed, a gruesome scene presents itself to the policemen in the cold storage room: Stefan Schneider, the driver, is sitting amidst the meat products,frozen to death in a most undignified manner. One thing is immediately clear: it was murder! The thermostat and the door handle have been tampered with. Next to the dead man, Hubert and Staller discover the letter "M" visibly scratched into the ice. Did Schneider use his last ounce of strength to leave a clue to his murderer? Or perhaps the perpetrator is leading them on a false trail? The police begin their investigation at the butcher's shop: everyone there is shocked by the employee's death; owners Annemarie and Martin Semmling were already missing Schneider. Markus Walter, who works for the Semmlings as a driver, is also upset. He claims to be the murder victim's best friend. And indeed, Hubert and Staller find out that the two often spent their breaks in the forest parking lot. But one thing makes the policemen suspicious: is Markus Walter really trustworthy? After all, the "M" in his first name matches the track in the ice. But what motive could Walter have for the crime? When Hubert and Staller make more detailed inquiries about the butcher's staff, they discover that the dead man's girlfriend is also an employee of the Semmling butcher shop. And on top of that, Markus Walter is her ex-boyfriend! Hubert and Staller have more and more doubts about the supposedly close friendship between the men. Did Markus Walter kill his "best friend" out of jealousy?