In 1910 she published The Dangerous Age (Danish: Den farlige Alder). It is the story of Elsie Lindtner, who, after divorcing her husband, attempts to rekindle a relationship with a younger man who had once worshipped her from afar. When this relationship fails as well, she resolves to spend her life traveling throughout the world with a female friend. The book created a great sensation, because it began to cut through tabooed themes like the sexual desires of a 40-year-old woman. The novel was translated into several languages, including English. It has been adapted into film several times, including a 1911 version directed by August Blom: Den farlige Alder, and a 1927 German version directed by Eugen Illés titled That Dangerous Age. In 1912, Michaëlis published a sequel to the novel named after the series' title character: Elsie Lindtner.
