Sarah Lancashire returns in the acclaimed BBC thriller written by Sally Wainwright. No-nonsense police sergeant Catherine Cawood is back heading up her team of dedicated police officers in the Calder Valley in West Yorkshire. While on duty, she makes a gruesome discovery - a body. The victims injuries bear a striking similarity to a string of other murders over the previous few months, suggesting a serial killer is on the loose. But the case becomes even more shocking when it emerges that Catherine knows the victim something that could have serious repercussions for both herself and her family.