S1, E3: Costley is shaken up, but won't tell Yvonne what happened inside Selway's flat. Yvonne asks him if they need to call the police. Costley tells her no; she just has to trust him. That evening, Yvonne is arrested for the murder of George Selway. Questioned through the night, she is forced to tell them about Selway's attack. Cleveland says Costley has already admitted their affair; momentarily thrown, Yvonne then calls his bluff and sticks to her story. To her relief, Yvonne is granted bail. Back home, she tries to explain things to Gary - why she didn't talk to him about the rape; and Gary, still ignorant of her affair with Costley, comforts her as best he can. At last, the first day of Yvonne and Costley's trial arrives. After a shocking account of the brutality of the attack on Selway, the prosecution call Witness A, "the MI5 man," to the stand. Yvonne is relieved that the truth about Costley is finally coming out - surely once the jury realise that he is an MI5 agent, they will better understand how he came to deal with Selway in such an extreme, but "efficient" manner. But Yvonne's world is blown apart yet again: Costley was turned down by MI5. The air of secrecy and mystery which had surrounded him had all been an act. Yvonne finally realises that she has no idea who Costley is. The man beside her in the dock. The man she trusted. The man on whom her liberty depends.