Harry Hole is rescued from life in Hong Kong as an opium addict to return to Oslo to help catch a serial killer.  He succeeds in traveling to the Congo twice where he finally kills the killer—-a formerly abused mad man who kills eight people in an attempt to cover up a murder staged like all of them by his childhood enemy.  Oy!  A strange and bizarrely twisting tale of evil in the snow.  Probably my last Nesbo!