1978. Cherkasov's group begins a new investigation: a young gamer Kira Miller and her lover Colonel Potapenko were killed at a dacha near Moscow. It turns out that shortly before her death, Kira lost 400 thousand rubles in a katrana - an underground casino. To find out all the circumstances of the case, Major Cherkasov decides to send Sonya Timofeeva to the katran. At the casino, Sonya meets Boris, nicknamed the Musician, who works there as a pianist. They have a whirlwind romance. But one day, ...