The first ep is confusing, as you need to get used to the backward storytelling, as well as the introduction of a lot of new characters. But this turned out to be a totally brilliant series. Some have dissed this series after only 1 ep (I ask you) which is just plain nuts. A few of the reviews just appear to be either seriously dumb, lazy or both. You have to make the effort with this and focus, but it's worth it as the pay-off is dramatic as well as tragic.
The acting of the 2 leads, Richard Dormer and Jodi Balfour is amazing as well as the chemistry between their 2 characters, DCI Gabriel Markham and DI Elaine Shepherd. They are investigating a brutal serial killer who likes to dowse his victims in acid. With each backward jump in time, you'd think there would be less known in the investigation, but actually as viewers we see and learn more. By the end of the 5th episode it's clear who the killer is, then in the finale we jump forward to where the 1st ep left off and move forward as normal, and what a finale! For me this was the best UK TV drama of the year. Nothing else even comes close.