Two Mules for Sister Sara (1970)

Directed by Don Siegel

When a wandering mercenary named Hogan rescues a nun called Sister Sara from the unwanted attentions of a band of rogues on the Mexican plains, he has no idea what he has let himself in for. Their chance encounter results in the blowing up of a train and a French garrison, as well as igniting a spark between them that survives a shocking discovery.