“When you read this message, delete this message.” With a small letter, without punctuation. Mother?! But how is this possible? Mom disappeared without a trace three years ago, and neither dad nor the police found any clues... And if it really is her, then why does she make herself known only now, when Nina has already learned to live with this emptiness inside? In every St. Petersburg passerby, there is a fourteen-year-old Nina sees his personal monster, a prehistoric monster: Basilosaurus, Prognathodon, Archelon. He sees and draws a person exactly like that. A mysterious message prompts her to start her own investigation in order to finally find out what her father, the investigator and her mother’s former colleagues are hiding from her, and to unravel the mystery of her mother’s disappearance. Evgenia Ovchinnikova begins the “Go and Come Back” trilogy with an exciting detective story. But this is not a pure example of the genre, where the center of events is a crime, but rather a psychological detective story, the main thing in which is the development of the relationships between the characters during the course of the plot.