Except for the final episode, which I will not describe, this series is among the best TV thrillers I've ever seen. Regional accents make some of the dialog difficult to follow if you're not a Brit, but the story line is quite clear. Although most of the faces were unfamiliar to me, the cast is excellent from top to bottom, a hallmark of BBC productions. Each of the twists and turns prior to the final episode was imaginable (if in a couple of cases improbable). But the last twist makes little sense in light of what went before. I would have rated the series a 10 if it had ended with the fifth episode (and a small coda). The final episode subtracted three stars from my personal evaluation. Bill Nighy, James McEvoy, John Simm, David Morrisey and Polly Walker were particular impressive in their respective roles.