Ellen Dorrit Petersen (Anita) and Fredrik Grøndahl (Martin) play mother and son in the film, a cinematic relationship they also portrayed in Troubled Water.
Fridtjov Såheim (Svein) and Laila Goody (Sigrun) play husband and wife in the film, which they also did in a theatre production of the play Iphigenia at the same time as the production of the film.
Kåre Conradi (Arild) and Ellen Dorrit Petersen (Anita), who play friends in the film, also playing husband and wife in the NRK TV-series The Conqueror, which was shooting at the same time as In the Dark.