Peggy Casey is preparing for a big weekend of fishing and her pub, Tigh Chasey, will be full to the door. She desperately needs the business. Summer is coming to an end and it has been a few months since it rained. As a result, the water level is extremely low. A body is found near the lake and it is a big story in the area. At first it is believed to be a bog body.

Detective Sergeant Frank Ryan is sent from Dublin, and what he discovers gives a disturbing insight into the history of the valley's damage, and the difficult relationships that bind Peggy and the three older members of the family.

Over the course of the weekend, Detective Ryan's investigation will not only reveal the terrible truth behind the dead woman's story, but will also reveal the deepest secrets of the Casey family.