Louis Theroux documents his investigation into what goes on behind the scenes of the infamous Church of Scientology.
As of right now (2017), there are two big documentaries on Scientology. This one, and the one made by HBO. Frankly, the HBO one is a bit better and definitely a must-see. This one is also good, and while it covers much of the same ground, it does go into other areas, too. Theroux, to his credit, seems to have very little fear of being arrested and gets some great footage near the base.
This film does have some strange narrative devices, such as casting actors in the roles of real Scientologists and then having them act out events that allegedly occurred. One scene in particular (in "the hole") is very effective. The casting of "Tom Cruise", unfortunately, never seems to go anywhere.