In 2004, the Swedish horror writer John Lindqvist published the first of his many novels, Let the Right One In. Set in the 1980s, it tells the story of a young loner in suburban Sweden who befriends a girl named Eli, who’s actually a boy and a vampire. The book quickly became a cult classic and has since been adapted for television, film, and the stage. The play, by Jack Thorne, makes its Manchester debut at the Royal Exchange Theatre. Bryony Shanahan directs. —Jensen Davis