The 4 ½ friends consist of three boys, one girl, and a dog. Kalle, the founder and leader of the detective office "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.

What happened at school that has all the kids upset? The disturbance is due to the mysterious break-in at the teachers' office!

The peculiar element of the case is the objects that the thief chose to take with him: two jars of raspberry jam, a teacup, a stopwatch, two books, and a bag of cosmetics. The only eyewitness is Fritz from the group of 4 ½ friends. And the most illogical element? The man that Fritz saw sneaking into the school at the time of the break-in bears a striking resemblance to the school principal. Is it possible that the principal is the main suspect in the case?

The 4 ½ friends are once again faced with an exciting mystery. Will they be able to solve it?