This new two part investigation opens with the team being put on a rather boring fraud case... they aren't on it long as DS Zailer decides to follow up when a woman she met at the gym tells her of 'a friend' who's partner claimed to have hurt a woman in the past. Zailer goes to the house she believes the woman is living and is shocked to find a body; it is the woman's husband. She claims not to have seen him for some time as she has separated from him. The investigation initially centres on the woman's new partner; a pianist who was involved in a fracas with the dead man a few weeks previously.
While the investigation is going on we also see the woman trying to find out just what her new partner did. He claims that something he did led to the death of a woman named Mary but refused to elaborate; arguing that she should trust him. She learns that he has other secrets when she follows him to London and catches him in the arms of another woman; a woman who looks remarkably like a photograph she finds labelled Mary.
This story featured solid performances from Olivia Williams and Darren Boyd as the leading detectives DS Charlie Zailer and DC Simon Waterhouse. Eve Birthistle and Theo James also do decent jobs as chief suspects Ruth, estranged wife of the victim, and Aiden, her new partner. The main story was suitably interesting although I could have done without the office politics back at the police station although it did need to some amusement in episode two. I suspect most viewers will have worked out who the killer is before the police; there aren't too many suspect and in this sort of series it is never the most suspicious characters that did it! Once the police figure out who did it the ending is fairly cliché even if it does feature some excitement. Still; it passed the time well enough.