The life of little Katya, the daughter of the investigator Mykola Zharinov, changes drastically when her parents and little sister Alisa die as a result of a shootout started by a gang. Being afraid that the mafia boss Zubov may decide Katya is an unwanted witness, her uncle, a professional burglar and safecracker, Hryhoriy takes her to live with him. Hence, Katya spends her childhood in a criminal den, without her family and old friends. Her old dream – to be a policeperson, just like her Dad – never comes true. Instead, Katya grows into am unstoppable go-getter Klara, who can pick any kind of lock and muddle any kind of brain.
One day, luck leaves Klara. The investigator Dmytro catches her, and she now she’s facing a prison sentence. To avoid it, Klara offers the investigator a deal. She’ll help him to find the serial killer named Ghost, who mysteriously penetrates into his victims’ homes and leaves them afterwards in the same unexplained manner. Klara, being able to “go through the walls” herself, finds the explanation of how Ghost does this. However, she doesn’t realize what dangerous game she’s dragging herself in, as Ghost, after he sees her bold interview on TV, decides to challenge her. Dmytro is put in charge of Ghost’s case. Dmytro is a charismatic and brutal young man, and Klara likes him a lot, though she refuses to admit it herself. Besides, not only do they fight every now and again, but Dmytro is also hopelessly married – while Klara has a principle to never mess up with married men.
There’s also Dmytro’s assistant – strict and principled Olesya, a recent trainee, who has her own motives to find Ghost as he’s guilty in the death of her fiancé. Despite Klara and Olesya’s relationship doesn’t go well at first, they eventually become friends. What’s more, Klara doesn’t even suspect Olesya is the daughter of Zubov, the man who ordered to kill her family. And Dmytro, the man she’s so attracted to, is her friend from her childhood, Dimka, with whom they used to dream to work at the police and have their own family one day…