Alexandra Simonova, a teacher at a city private lyceum, is fascinated by the father of her student, Sarah, an American businessman of Russian descent, Jeff Collins. The lyceum's director, Pyotr Pavlovich Pokatilov, is secretly in love with Alexandra and is not happy with her friendship with a foreigner. He tries in every possible way to annoy her with petty quibbles.
Alexandra and Jeff enjoy each other's company. They have a relationship. Sara likes to study, she is girlishly in love with her mentor Alexandra, and copies her in everything.
Tatiana Kulik, an investigator for particularly important cases at the city prosecutor's office, and her husband Igor Kulik, a university lecturer, after desperate attempts to have a child, find a woman to carry their child — a surrogate mother, Lida Oleynikova. Lida works as a dishwasher at a lyceum. A man nicknamed the Commander also goes about his business. He runs his own security firm, Aegis, and has many wealthy clients who need protection.
But one day, the fates of the heroes intertwine.
The lyceum receives disturbing phone calls — students with signs of poisoning by an unknown toxic substance have been taken to the city hospital. Some of the children are in serious condition. All the victims are from Alexandra Simonova's class. Jeff received the same message. His daughter Sarah was among the victims.
The city authorities, concerned about the mass poisoning of the lyceum students, are doing everything they can to prevent the press from turning this event into a high-profile one. The prosecutor's office opens a criminal case, and the investigation of the crime is entrusted to the most experienced officer — Tatyana Kulik.
From this moment on, the measured everyday existence of all the characters comes to an end. Events, one more inexplicable than the other, overtake them every day.