When DI Ben Kitto sees a baby thrown into Penzance harbour, he prays it's a trick of the light. But the threat is real. The child survives – barely – and soon a chilling pattern emerges. As the Burning Sky Festival brings dancers, dreamers and stargazers to Cornwall's coast, children begin to vanish. A small mermaid figurine is found beside each scene, echoing the legend of the Mermaid of Zennor, who lured a man to his death beneath the waves. Still reeling from a devastating bereavement and determined to protect his young son, Ben is pulled into a deadly investigation. Then the killer's messages begin arriving at his home. As the summer solstice approaches, Ben must confront the boundaries of love, loss and obsession. In a final, desperate chase along the headland, only his bond with Noah – and the loyalty of his dog, Shadow – can prevent tragedy from repeating itself.