The Last Secret for Three

"In the life of Senior Lieutenant Sofia Svyatova, a dark streak has begun — darker than ever. First, Sofia found out that her beloved Captain Evgeny Melikhov was cheating on her. Then the closest person was killed — her sister Antonina, and Sofia, as the sole heir, found herself under suspicion.
Melikhov is also grieving: his new girlfriend died under suspicious circumstances, the investigation of which the captain is not allowed to pursue. The former lovers, sidelined from the investigation, must unite to find the real criminal together…"