Filmmaker Thierry Guetta had been casually documenting the underground world of street art for years, but when he encounters Banksy, an elusive British stencil artist, his project takes a fascinating twist. Unimpressed with Guetta’s footage, Banksy takes over filmmaking duties and Guetta reinvents himself as a street artist named Mr. Brainwash — and, much to Banksy’s surprise, immediately becomes a darling of the Los Angeles art scene.