Herman Wallace may be the longest-serving prisoner in solitary confinement in the United States — he’s spent more than 40 years in a 6-by-9-foot cell in Louisiana. Imprisoned in 1967 for a robbery he admits, he was subsequently sentenced to life for a killing he vehemently denies. “Herman’s House” is a moving account of the remarkable expression his struggle found in an unusual project proposed by artist Jackie Sumell. Imagining Wallace’s “dream home” began as a game and became an interrogation of justice and punishment in America. The film takes us inside the duo’s unlikely 12-year friendship, revealing the transformative power of art. By Angad Singh Bhalla.