Kristiansson and Kvant are original characters from the Martin Beck novels by Maj Sjöwall and Per Wahlöö, in which both are male. This is the first time they appear in the series.
There are key plot similarities between this and the fourth Martin Beck novel by Maj Sjöwall and Per Wahlöö, "Den skrattande polisen" ("The Laughing Policeman") - the title of this translates to "The Crying Policeman".
Valter Skarsgård is the son of Stellan Skarsgård. Stellan played Carl Hamilton in Täcknamn Coq rouge and Den demokratiske terroristen. Peter Haber took over that character in the tv series Fiendens fiende.