On the Feast of St John the Cornish villagers of Trevennick dance around midsummer bonfires and make offerings to the river. It's not the sort of thing that appeals to Audrey Delaney. But when her (sort of, almost) boyfriend Noah whisks her away on a surprise trip to the West Country, she's determined to do the best she can to enjoy herself. Then their first night ends in tragedy, and Audrey finds herself stuck in the back of beyond, embroiled in a police inquiry, and unsure who to trust. Not Noah, who obviously had an ulterior motive for bringing her here. And certainly none of the villagers: brooding mussel farmer Trevor, weirdly intense vicar Lamorna, and infuriatingly cocky and omnipresent jack-of-all-trades Griffin. She'll have to untangle the mysteries of this insular community quickly, though, because people are dying fast. The river will have its due...