The BAFTA-winning hit returns, as Cassie (Nicola Walker) and Sunny (Sanjeev Bhaskar) investigate a cold case with alarming links to the police force. A corpse is discovered in a scrap yard, his features frozen in time. Four suspects emerge. All four have links to the law and attended the same police training course back in 1989. Since then their lives have gone in very different directions. The volatile chief superintendent with a point to prove and a past to forget. A seemingly successful businessman with a criminal past. A Cambridge-educated high-flying cop in a toxic relationship with her mother. And the daughter of a policing family, pushed into a career she cannot stand. All now in their late forties, the police investigation has the potential to shatter their reputations, family relationships and the lives they've built over the last 30 years.