A cold murder case from 1990 brings detective superintendent Elizabeth Bancroft and DS Katherine Stevens together.

Bancroft helps Katherine and Anya with the Fraser case, but they are struggling to find any decent forensic evidence; Katherine and Joe's relationship progresses.

Bancroft faces a startling blast from the past that brings the events from 1990 back to the surface. Meanwhile, Katherine wrestles with twists and turns from the new information she is uncovering. Bancroft secures Zaheera in safe accommodation, and Daanish fulfils his part of the deal. Anya makes a surprising visit to an old friend. Katherine confronts a chilling truth.

Katherine and Anya make a determined push to get to the bottom of the Laura Fraser case once and for all, hatching a plan to get the DNA evidence they desperately need. Bancroft executes a massive sting operation against Athif Kamara, but all doesn’t go smoothly. Bancroft is forced to reveal carefully kept secrets about her past. The truth about what really happened to Laura Fraser comes to light.

Promoted to detective chief superintendent, Elizabeth Bancroft has achieved professional success but at great personal cost. When a double murder brings an unexpected reunion, Elizabeth is forced onto the sidelines by Detective Superintendent Jake Harper. But as new enemies emerge, old foes make their move.

The evidence around the murders points the team in one direction, but the disappearance of the prime suspects escalates Elizabeth's own investigations. With Bevan managing the Kamara deal, Walker gains a lead in his case against Bancroft. As the walls close in, Elizabeth acts to take control.