Matt is intrigued when his partner Liz brings home an old carpet bag she found dumped in the local library. It contains a pile of mysterious handwritten notes. Liz is convinced the bag belongs to Old Molly, a local woman who lives on the streets. The following day, a body is discovered in a marshy lagoon. It's Old Molly. Suffocated with an expensive men's handkerchief. Molly clearly knew something that got her killed. Liz believes she was trying to tell them something important. She calls on her nephew David to help decipher the carpet bag notes. Meanwhile Matt is hired to find teenage runaway Liam Cooper. Liam has been missing for ten days now, and Matt has a very bad feeling about him. A few days later, a second body is discovered in an old barn out on the fens. Matt and Liz must piece together the cryptic clues Molly has left for them before more people die. The answers lead to the remote fenland village of Marshdyke-St-Mary - and a series of shocking secrets stretching back many years.