The main character of the story is 12 year-old Denis, a fan of actor Arnold Schwarzenegger and a faithful admirer of his films. The summer holidays begin. Most of Denis’s plans for the summer fall through. He regularly goes to the movies, gets together with friends who have remained in town, and unenthusiastically, but nonetheless, takes cake of his dog Arnie when his mother, a television journalist, is too busy. Taking his dog for a walk one evening, Denis witnesses the loading of harmful substances at a local chemical plant. A series of slightly unusual circumstances, holidays with boy scouts, a new friend - private detective Emil, his mother’s environmental contributions in TV shows and a longing for adventure lead Denis to follow the perpetrators, who unload the wastes in a national park. Denis’s adventures end happily for him and for all his family members, while the criminals are punished - as they should be.