Two Mules for Sister Sara might have worked. But with Clint Eastwood as one of the mules, an American mercenary looking for a fast peso in old French-occupied Mexico, Shirley MacLaine as a scarlet sister disguised in a nun’s habit, and Don Siegel’s by-the-old-book direction, it doesn’t.
Screenplay based on a story by Budd Boetticher, needed a Lee Marvin, or a portrayal like Humphrey Bogart’s in The African Queen to work. MacLaine is literally unbelievable as a nun, and the story’s main thread of tension, the relationship between her and Eastwood, simply dissipates.
Siegel and Mexican cameraman Gabriel Figueroa use the Mexican locations to great advantage, with sweeping panoramics of the brutal countryside and intriguing settings.