‘The Leader’ Review: Tim Blake Nelson and Vera Farmiga Are Creepy and Powerful in a Disturbing Drama About the Heaven’s Gate Cult

"The Leader," as a dramatic experience, is creepy as hell, but as written and directed by Michael Gallagher, it’s also authentic and sharply told, and it’s inquiring about the right things — namely, why would people descend to this, and what, if anything, does it have to say about us?