Ksenia Averintseva, a world-famous cellist, buys an apartment overlooking the Griboedov Canal. When her grandmother hears about it, she dies from a heart attack. By a fateful coincidence, the grandmother had lived in that old apartment and had been a suspect in an unsolved case. But Ksenia can’t believe that her grandmother is a murderer. She asks Maria Karavai for help, and Maria agrees. Gradually unraveling the secrets of the communal-house residents, Masha and Ksenia get closer to the main secret—deadly dangerous not only for the past, but also for those alive now. What began as an amateur archival investigation turns into a high-tension thriller. Hiding in the maze of St. Petersburg courtyards and in old forts near Kronstadt from the killer hunting her, Maria Karavai tries to find the lost, time-locked information piece by piece…