Elena Zoric, a sex worker and addict, is murdered, her body concealed and left near a stream in North London. Her phone lies nearby, the last number dialled was to a former NCA Investigator, a woman who had saved her from sex trafficking: Met DI, Grace Archer.

When questioned by North London police, a devastated Archer has no answer to why Elena would call her moments from her death. Archer wants to lead the investigation but its out of her catchment area and she is warned off it by her new boss, the charmless old school copper, Chief Inspector Les Fletcher.

The thirty year old remains of a woman are found in the attic of an abandoned house. Archer takes over the case and discovers the victim died in similar circumstances to Elena Zoric. Archer pushes for an alliance with her North London colleagues but it seems they have other priorities than looking into the murder of "a drugged up prostitute". An incensed Archer goes rogue and searches for proof that both women were murdered by the same man.