Calling Card (S01E02)

Jack and Charlie dive into an assault case involving the owner of the Green Pit nightclub in east London, only to find the victim's sister unconscious in the cellar, bleeding from a head injury. Their investigation becomes challenging due to the absence of CCTV footage. Things get more complicated when they discover the body of a 19-year-old student, who has a nightclub flyer tucked in his pocket, adding a new layer of mystery to the case.