Following the stabbing of an officer on the base, Eliza warns Amy to get control of her investigation. Amy must find the traitor in the ranks of the Air Force. Kirsten, now working with MI5 partner Ramsay, uncovers key evidence linking a squadron member to the attack. With the force running out of leads on Chapman's killer, Kirsten follows a hunch. Amy takes a grave risk that puts her in jeopardy.

In the aftermath of a brutal rescue mission Amy is questioning everything. She is convinced that what she's believed up until now has been a lie, but all the evidence points the other way. With Amy completely isolated, Kirsten begs her to come home, but Amy can't let go of her suspicions. Despite huge pressure from above, Amy refuses to leave Wudyan, putting herself in grave danger.