Talented mathematician Anna Nikolaevna Shvabrina works as a school teacher. By the will of fate, she begins to help Captain Vershinin investigate complex crimes using mathematical methods. The main tools of the investigator are many years of experience and the basics of forensic science, Anna Nikolaevna is an impeccable knowledge of mathematical methods, formulas and models. It would seem that they are completely different, but it is thanks to this union that it will be possible to investigate the most difficult cases.

Night in the center of Moscow hit by a girl, she urgently needs complex operations. Her friend Kira finds the culprit, arrogant and cynical tycoon Sergei Polanski, who refuses to admit his guilt and help the injured. He does not care, he has everything under control. In desperation, Cyrus turned for help to the three guys sympathetic to her - bykovatomu Fede, arrogant, handsome Artem computer genius and his wife. Boys entered into between the Covenant - "help the girl punish the villain, and then decide who will become her boyfriend."

Three generations of the family lived all together. But then everything changed. The grandma remained alone, her granddaughter visits her less and less and her daughter doesn’t see her at all. A moth appears in the flat of the old woman and it is impossible to get rid of her. Because the moth is the loneliness.