A newly-retired detective from the Met is murdered in a murky alley in Edinburgh, a sinister calling card left with the body. The dead man had been a close friend of psychologist Tasha Phillips, giving her her first gig with the Met decades before. Tasha begs DI Yvonne Giles to aid the Scottish police in solving the case. In unfamiliar territory, and with a ruthless killer haunting the streets, the DI plunges herself into one of the darkest, most terrifying cases of her career. Who exactly is The Poet?