Young Moscow professor Marina comes to rest in a sanatorium on the Volga . She dreams of an adventure, maybe detective, at worst, romantic. And gets everything in the first slot in one bottle . The wind took her hat to the pond, and, pulling it out, Marina saw a drowned man in the water. The police considered it an accident. But Marina's sure it's murder. She noticed a strange detail... But with whom to share? She tells her secret to Fedor Tuchkov, who at first was considered a cretin, and the next day he became her partner . A resort romance is brewing, which she resists with all her professorial strength. But then another vacationer dies, who knew something about the drowned . Marina has nothing left, how to trust Tuchkov again, especially since it turned out: he is a professional ...