The BAFTA awarded crime series is back with it's fourth season. This time Detective Cassie Stuart and her partner Sunny Khan are confronted with a case where the bodies have a disturbing link with the police. After finding a dead body at the dump, Cassie and Sunny come across four suspects who joined the samen police academy as they did in 1989. The suspects all left since then, some have build a successfull life while others are struggling. As Cassie and Sunny dive deeper into the case they struggle with the outcomes of their investigation. Can they always trust the police? Are the two detectives willing to destroy their colleagues lifes just to find the truth?