Shona Sandison might be about to get her biggest scoop yet – if she can make it to the end of the investigation alive. In a darkening, post-COVID world, fearless investigative reporter Shona Sandison is seeking meaning – and her next big story. A secret contact inside the government has promised her something huge, but she has no idea of the danger she is in. Meanwhile, her old friend Hector Stricken has taken on a position in communications for a new state agency, where he stumbles across a sinister, top-secret project codenamed 'Grendel'. And on the Scottish coast, an ageing spy chief, living in seclusion, grieves his murdered son – and contemplates revenge. Connecting them all is an insidious conspiracy within the UK's most powerful institutions, a rot so deep that the only way to cure it may be to cut it out – or burn the whole thing down.