There's nothing wrong with this show. Much like the show The Missing it graphically illustrates the distress of a family desperate to know what happened to their missing little boy. It has numerous twists and turns and is, as usual, brilliantly acted. Having said that, however, I'm docking this piece a point for the aggressive use of flash-backs, which confuse rather than enlighten, and, in my opinion, were unnecessary. They could have been inserted chronologically in an initial time-line. I'm also docking a point because the passage of the show doesn't really surprise. As a consequence it works for its date of production perhaps, but hasn't any legs. If this is the type of BBC/E-One thriller/who dun it production you enjoy then you won't be disappointed, but if you are arriving at this show from a more modern perspective there is a risk you'll be bored.
I do like this type of British drama however, and had no real problem with it, and certainly wasn't bored.