Leopold Wallisch, nick-named "Lemming", was fired from the homicide department due to intrigues by his colleague Krotznig. Now he works for a small Viennese private detective agency and spies on potential adulterers. When the Latin teacher Grinzinger is murdered while under Lemming's observation, he gives himself a shove and decides to solve the case himself. "Lemming's First Case", an adaptation of the best-seller by the Austrian author Stefan Slupetzky, promises pure crime comedy.
To reveal the secrets of a photo and a postcard of her late mother, the art historian Lena goes to St. Veit, where she wants to climb the Simonskopf. To do this, Lena first has to learn to climb. The attractive hotelier and mountain guard Martin helps her overcome her fear of heights. The two fall in love. Then it turns out that Martin's father and Lena's mother knew each other very well.