Johan works at a laboratory, where his boss never calls him by the same name twice. One day, he discovers that one of his neighbors, Bengt, has left his little daughter, Pia, in his care, since he's on the run from the two clumsy villains Kurt and Felix. Johan had not been counting on taking care of a little girl, when he's got his job to think about, especially not when he discovers, that she's much more difficult to deal with than he had expected. When Johan falls in love with another neighbor of his, Marie-Louise, who has just moved in, and Kurt and Felix start sneaking around his apartment, it gets even more complicated for him to be saddled with this girl.