AC-12 link Gail Vella's murder with a historic case of police corruption, and Kate hatches a plan to tell once and for all if Jo is bent. They are closer than ever to cracking the case, but when Hastings' authority is undermined it leaves his team in a potentially dangerous situation.

Cast: Ace Bhatti, Shalom Brune-Franklin, Martin Compston, George Costigan, Amy De Bhrún, Adrian Dunbar, Perry Fitzpatrick, Kelly Macdonald, Anna Maxwell Martin, Vicky McClure, Alastair Natkiel, Andi Osho, Gregory Piper, Owen Teale