A man falls to his death in western Scotland. From a distance, another man watches. He approaches the body, tucks a book into the dead man's pocket, and leaves. When the Scottish police show visiting Detective Chief Inspector Domenic Jejeune the book, he recognises it as a call for help. Back in Saltmarsh, the brutal murder of a researcher has everyone looking at the man's controversial studies as a motive. But Sergeant Danny Maik believes a huge cash incentive being offered for the research may play a crucial role. With their Chief Superintendent blocking every attempt to interview the project's uber-wealthy owners, Jejeune and Maik must work together to find their answers. But will the men's partnership survive?