The 4½ friends consist of three boys, one girl, and a dog. Kalle, the founder and leader of the detective agency "Kalle and Sia," the twin siblings Steffi and Karlsson, Fritz, and their dog, Pippi, get involved in various adventures in their attempt to solve mysteries and strange cases.

Berti, the son of the responsible class teacher, disappears from the campsite in the middle of the night without leaving a trace! Only his socks remain at the scene. Could his disappearance be related to the amber figurine they discovered? The group is disturbed. Then Kalle has a brilliant idea: he puts one of Berti's dirty socks in Pippi's muzzle. And indeed, visibly disgusted by the stench, but also determined, Pippi begins to search for clues...