Library mystery

Books are going missing from the local library and the librarian doesn't know how to deal with the thefts. The investigation is complicated by a mystery that has everyone scratching their heads. Could this be a case for the perfect team of young detectives?
Lenka, Ula, Aleš and Petr love strange mysteries and thrilling detective stories. When they find out that something particularly mysterious is happening in their library, they don't hesitate for a moment. Will they manage to solve it? The detective investigation is about to begin!