I watched this DVD last night. In the Realms of the Unreal: The Mystery of Henry Darger (Thank you Netflix for carrying what the local stores won't).
Its the story of a man, mostly alone in the world from a very young age. A functioning member of society, living here in Chicago for most of his life. Upon his death, his landlords discovered what it was that Henry did in the evenings. His room contained a 15,000 page novel of epic proportions that Henry had been working on. They also discovered hundreds of remarkable drawings and painting illustrating his opus.
Darger had no family and so the film focuses on the small amount of info his landlords and caregiver can provide.
Here is a brief excerpt from the films homepage.
This innovative feature length documentary, directed by Academy Award-winning filmmaker Jessica YU and produced by Susan WEST, explores the parallel lives of legendary outsider artist Henry Darger. Reclusive janitor by day, visionary artist by night, Darger’s 15,000 page novel details the exploits of the Vivian Girls, seven angelic sisters who lead a rebellion against godless, child-enslaving men. Featuring the voices of Dakota FANNING (I AM SAM, CAT IN THE HAT) and Larry Pine (THE ROYAL TENENBAUMS, THE ICE STORM), the music of Emmy-winning composer Jeff Beal and the work of a team of animators, this wholly original film tells the story of a hidden universe.

