FBI agent, Rachel Walling gets the call she's dreaded for years - 'the Poet' has returned. She worked on the famous case, tracking down the serial killer who wove lines of poetry into his hideous crimes. She has never forgotten Robert Backus, the killer who called himself - The Poet. Harry Bosch gets a call, too. The former LAPD detective hears from the wife of an old friend who has recently died. The death appeared natural, but this man's ties to the hunt for the Poet make Harry dig deep - and lead him into a terrifying, bewildering situation.