Desc: Ryttare i blått: Directed by Arne Mattsson. With Gunnel Broström, Bengt Brunskog, Gio Petré, Björn Bjelfvenstam. When private eye John Hillman is on assignment in London his wife Kajsa visits the Army's riding school at Strömsholm, Sweden. She gets involved in the strange murder of the Blue Rider. Unknown to everyone at Strömsholm.