Knife is the 12th novel in the Harry Hole series, and as the novel begins, Harry awakes ferociously hung-over, his trousers covered in blood, reputedly the result of a fight in a bar. His beloved wife, Rakel, has ended their relationship but he has been accepted back into Crime Squad, working on what he calls "entry level material", sorting out paperwork and cold cases.

He would rather be investigating the murders of three women in Sweden and Denmark because Svein Finne, sexual predator and serial killer, is free after a decade in prison. However, the head of Crime Squad asks him, "If you were running Crime Squad would you send a drunk unstable detective to talk to our already skeptical colleagues ... who have pretty much made up their minds that the same man isn't behind the murders in their cities?" But Harry won't give up because his obsessive search for the worst offenders in society was his only reason for living, until he met Rakel.

Nesbo has recently described his Harry Hole series as "a tragedy ... I have to go with that". In Knife, therefore, Nesbo answers his own question: "What is the most terrible thing that can happen in the life of our main character?" and so in chapter five, Harry learns that Rakel has been murdered.

Harry, obsessed with Svein Finne believes that he has killed Rakel. Finne was Harry's first arrest as a young detective and Harry has been responsible for the fact that Finne has spent 20 of his 70 plus years behind bars.

When he is denied access to the investigation, Harry goes rogue, helped by his old friend Bjorn Holm, a forensics officer, Kaja Solness, who rescued him from drugged despair in Hong Kong and Alexandra Sturdza at the Forensic Medical Institute. When Alexander runs Finne's DNA through the database, she discovers he's the father of Valentin Gjertsen, one of the worst killers in Norwegian Criminal history who Harry killed in The Thirst, Harry believes he has discovered Finne's motive for murdering Rakel.

What follows, in perhaps an overly long investigation, is pure Nesbo; a roller coaster ride through a complex twisting plot, in which Harry is taken to the absolute brink of despair as he pursues an elusive, sadistic, amoral villain.

Knife is a dark, cruel tale of guilt and revenge.

Be warned. Nesbo has said "It's not my job as a writer to be nice to my readers" and in Knife he definitely isn't.