Fresh testimony launches AC-12 back on the trail of a corrupt officer.

Loyalties are divided when DS Steve Arnott comes under scrutiny from his colleagues.

DS Steve Arnott is arrested on suspicion of murder but continues to protest his innocence.

As AC-12 wrestle with the new forensic evidence casting doubt over Tim Ifield, Kate is approached by another woman claiming to have been assaulted by Michael Farmer.

Roz's husband Nick is brought in for questioning by AC-12. But while Nick denies any involvement in Steve's attack, his suspicions about Roz mount.

DCI Roz Huntley struggles to allay her husband's suspicions. AC-12 find a new angle to pursue their case against her.

While Nick Huntley faces lengthy questioning, AC-12 remain convinced of Roz's involvement.

Following the deadly hijack of a police convoy, AC-12 target a ruthless organised crime group known to have links with corrupt officers.

Kate and Steve attempt to track down a lead. A fresh police leak enables another audacious raid, while Steve’s attempts to gather information put him in a dangerous situation.

Corbett's most daring plan yet requires McQueen to exploit links with corrupt police officers.

Tensions rise in the OCG following the events at Eastfield. With troubling questions hanging over the identity of ‘H', suspicions mount at AC-12.