Adapted from the books of novelist Mark Billingham, `In the Dark' follows Detective Inspector Helen Weeks, as she embarks on an extremely personal investigation. She is forced to return to her home town of Polesford, Derbyshire, with her partner and fellow detective Paul, to examine the abduction of two girls. The primary suspect is the husband of her childhood best friend, Linda, and the race is on to discover whether or not he is guilty. Along the way, the series also delves into Weeks's past, to uncover why she has been avoiding Polesford for so many years.