"Detective sergeant Timo Harjunpää of the Helsinki Violent Crime Unit loses his daughter in a tragic way. Despite the support of his closest colleague, Constable Onerva Nykänen, Harjunpää is unable to recover from the loss of his family. He seeks revenge against his daughter's killer, while in his work he investigates strange deaths in the Helsinki metro that turn out to be the work of a serial killer."