There is excitement in the air as the travelling theatre arrives in Seal Bay. When The Spriggan Travelling Theatre Company arrives in Seal Bay to perform a Cornish version of King Arthur the locals flock to be entertained. But for Morwenna Mutton, sexagenarian librarian, wild swimming enthusiast and amateur sleuth, the theatre brings intrigue too. Actor and director Daniel Kitto is not the most popular member of the cast and unbeknownst to him, his role of Uther Pendragon on the opening night is to be his swan song. In front of a horrified audience, he collapses during the dying moments of the performance in a pool of fake blood, and although the police are content that the causes of his death are natural, Morwenna isn't so sure. And once it becomes clear that there are a number of people who stand to gain from Daniel's death, Morwenna's investigation takes a dangerous turn.