A new witness comes forward claiming to have crucial evidence in Gail Vella's murder. Kate is torn between her loyalty to Jo and to AC-12.

Cast: Ace Bhatti, Nigel Boyle, Shalom Brune-Franklin, Martin Compston, Amy De Bhrún, Tara Divina, Adrian Dunbar, Rosa Escoda, Perry Fitzpatrick, Tommy Jessop, Kelly Macdonald, Vicky McClure, Kerri McLean, Andi Osho, Gregory Piper