It seems that Masha Nesterova can only be envied. Of course: together with their mother they moved to a small village on the shore of a warm sea. But at school a real war is declared on the new girl, and the busy mother is in no hurry to help her daughter. Do you really have to be sad alone? And then something begins to happen around her that Masha involuntarily forgets about her troubles. For no apparent reason, a young guy falls from a cliff, a mysterious thief sneaks into an empty boarding house at night... What if these events are connected? And somewhere nearby there is a dangerous criminal wandering around? Well, at least Masha has a new friend - Senya. Never mind, together the young detectives will figure it out!