When originally published, the series was simply titled Batman: The Dark Knight, with a different subtitle for each issue (The Dark Knight Returns, Dark Knight Triumphant, Hunt the Dark Knight, and The Dark Knight Falls), but when the series was collected into a single volume later that year, the title of the first issue was applied to the entire series, and has remained so ever since. Some of the earliest collected editions also bore the shorter series title. The story introduces Carrie Kelley as the new Robin and the hyper-violent street gang known as the Mutants. In the Pre-"Flashpoint" DC Multiverse, the events of "The Dark Knight Returns" and its associated titles were designated to occur on Earth-31.