As other reviewers have mentioned, the acting and plot are at a high standard, making for a believable and gripping drama series. There are interesting side stories, often red herrings to the main plot - but you don't know that at the time. My only reservation is that this being a BBC drama, it wasn't too hard to guess the trajectory of the case and who the culprits might be. The Beebs 'usual suspects'. That slightly devalued the twists and turns in the plot for me.