Baba (Dipo Ola) is working as a nightclub toilet attendant when he meets the magnetic Freddy (Hermione Corfield) as she stumbles into the gents with her date, Simon (Nigel Harman).
There's an immediate connection between the two of them. When Baba witnesses Freddy's date try to sexually assault her something in him snaps. Baba is a former child soldier able to inflict tremendous injury quickly and efficiently, much to his shame.
Freddy has to step in to stop Baba killing Simon, but rather than being horrified, she is drawn to this tortured man.
DS Lola Franks (Eve Myles) has been partnered up with new-to-the-squad DI Jackson Mendy (Babou Ceesay). DS Franks is wary of her new partner: he's a homicide novice and worked in anti-corruption, plus he believes there's no such thing as free will - that we can't ever be held entirely responsible for our actions.
Jackson's determined to win Lola over as they get stuck into the first case: a man who's been found handcuffed to his bed and stabbed in the back of his neck.
In the explosive first episode, we follow two timelines simultaneously, swapping between Baba and Freddy's deepening relationship and the start of DS Reid and DI Franks' investigation. The hunt is on.