Harry Kvist walks out the gates of Langholmen jail into the biting Stockholm winter of 1935. He has nothing to his name but a fiercely burning hope: that he can leave behind his old existence of gutter brawls, bruised fists and broken bones. But the city has other ideas. Nazis are spreading their poison on the freezing streets, and one of Kvist's oldest friends has been murdered. Before he can leave Stockholm's underworld for good, he must track down the killer. As Kvist uncovers a trail of blood leading to the highest echelons of Swedish society, the former boxer finds himself in a fight to the death with his most dangerous opponent yet.

It's summer in Stockholm, and the city is sweltering in the grip of a rare heatwave while fascists and communists beat each other bloody in the streets. Harry Kvist has had enough. It's time for him to leave. But first he has some business to take care of. His old friend and ex-lover, Reverend Gabrielsson, has been murdered, and the police are more interested in anti-Semitic rumours than finding the truth. Kvist investigates the only way he knows how, with his fists, uncovering a Nazi terrorist plot and a cabal of corrupt cops. Before long he finds himself caught in the middle of a turf war between two of the city's most brutal gangs. Can he fight his way out of one last corner and find a way to freedom, or has Kvist finally taken a punch too many?