This miniseries proves that your plot and character development don't have to be tight as long as you have solid acting, directing, and overall dialogue. The show starts with two separate stories, each with its own intriguing juxtapositions, which you can easily predict will become intertwined: 1) a criminologist on death row, and 2) a vicar who is covering for a suicidal paedophile working in his church. Even though you know these two plots will be intertwined, the ways in which they become intertwined are still surprising. Other strengths were camera work and pacing. There were some interesting shots and transitions that helped tell the story. The scenes cut between the two eventually intertwined stories at the right moments to reveal information without feeling gimmicky or deliberately leaving the audience in the dark just for a big reveal. The pacing never felt like it lingered too long on anything and didn't spend too much time on subplots. In fact, everything that seemed like a subplot ended up being in service of the main plot. Though that's more a strength of writing, it made the pacing feel fast enough to keep the audience engaged but slow enough to let emotions develop and information sink in. 

As a caution, the content is very dark at times. You're dealing with pedophilia, extreme violence, captivity, and mutilation all in one 4-episode story. And it often handles these topics with a shade of humour. 

Really, if the inciting incident had been more believable and/or better explained through more solid character development, this would have been a 5-star series.