The series is basically split between Travers's and DI Wenborn's investigations. It is an incredible study in contrasts. For while Travers is compassionate, intellectual and sophisticated, Wenborn is his exact opposite. He's not above threatening or blackmailing individuals to get the information he needs and is generally a nasty piece of work. As his superior says to a junior officer whose been partnered with him, don't take it personally, the guy hates everybody. Even their home lives are completely opposite. Travers is a dotting father and loving husband who's happiest in the bosom of his family. Wenborn on the other hand is emotionally abusive to his wife to the extent she's started shop lifting and the only time he pays attention to his infant daughter is to tell his wife to make her shut up. All in all we know which of them we prefer.
So when Wenborn starts to find circumstantial evidence tying Travers to the murder of his former client you don't want him to succeed in building a case against him. For even if Travers is guilty, the idea of this little creep taking down such a nice guy feels wrong. Especially as the man who was murdered could still have been guilty of killing a little boy. Although he was found innocent by the jury, there was still plenty of evidence that pointed to the activist's guilt. Yet, should that matter if Travers is guilty? Where's the justice in somebody taking the law into their own hands?
What's amazing about this series is how it manages to raise these questions about the nature of justice while telling the story of the two investigations at the same time. It's like watching a top notch detective story and a debate on morality at the same time. Even better is how the show's creator's have managed to handle this without ever throwing the subject up in your face. Not once do any of the characters talk about it, yet it's an ever present subtext which comes out through the natural development of the story and the character's behaviour.
Both Purefoy as Travers and Creed-Miles as Wenborn, do exemplary jobs in their respective roles. While it's easy to hate the police officer for the creep he is, we also come to have a little bit of grudging respect for him as he doesn't care who he pisses off, he just wants to solve the crime. While he may have very few redeeming qualities as a human being, as his boss says, he gets results and usually catches the crooks with strong enough evidence to make a conviction stick. Travers on the other hand is someone we like and admire. Yet Purefoy's performance is such that we know there is something wrong with him. He seems like he's holding himself just a little too tight, or saying he's fine as if he's trying to convince himself as well as the person asking him. When we start to see what he's hiding, those moments he lets his guard down, it still doesn't make him any less likeable, and in some ways even increases our sympathy towards him.