In William Greaves’s experimental, improvisational masterpiece, a second film crew documents the first while they record a series of actors reenacting the same breakup scene over and over again. Tempers flare and complications abound as the struggling crew rebels against Greaves’s refusal to define and chart the direction of the project. Set in Central Park in 1968, this cultural landmark is an insightful and riotous observation of the psychology of performance and the madness of moviemaking.