Who is Rydberg in the novel, Faceless Killers?

Rydberg is a thorough investigator and one of the men on the force that Wallander both likes and trusts the most. Rydberg has rheumatism in his leg that bothers him and is supposed to retire in a couple years. He learns that he has cancer during the course of the book, and Wallander realizes that he is losing one of his friends, not just a colleague. Like Wallaner, Rydberg is depressed at the changes he sees in society and the tendency for increased violence in crime.