Plot
Just after the American Civil War, a former Union soldier named Hogan rides up on a naked woman about to be raped by bandits. He kills the bandits, and the woman dons a habit, revealing herself as a nun. Sister Sara begs his continuing protection from French soldiers who are tracking her as a known Juarista, raising money to assist Mexican revolutionaries fighting French occupying forces. When Sara requests that Hogan take her to the Mexican camp, he is at first hesitant to deviate from his plans, declaring that if she were not a nun, he would let her fend for herself. Learning that she has knowledge of the French garrison where she has ostensibly taught Spanish to the French soldiers, Hogan agrees to escort her there, as he had previously arranged to help the revolutionaries attack the French garrison in exchange for half the garrison's treasury.
As the duo heads towards the camp, evading French troops all the while, Hogan is surprised that the nun swears and drinks whiskey. While on their way to destroy a French ammunition train, Hogan is shot at by Yaquis and seriously wounded with an arrow. To anesthetize him while removing the arrow from his shoulder, Sara plies Hogan with whiskey, making him drunk in the process. Due to his injured shoulder, Hogan cannot climb the trestle. When Sara declares she cannot climb the high trestle herself to set the charges, Hogan reminds her of her debt to him in saving her life, and she reluctantly complies, enabling them to successfully blow up the train. In his drunken stupor, Hogan bitterly reveals to Sara that he is attracted to her and resents her being a nun.
Eventually, the two reach Juarista commander Col. Beltran's camp. In the lead-up to the attack, Sara begs the local villagers for money needed to purchase dynamite for the assault on the garrison, enlisting the help of prostitutes at a brothel. When Hogan is shocked that she would take them to a brothel, Sara reveals to Hogan that she is not a nun, but a prostitute and a Juarista wanted for shooting a French lieutenant. She posed as a nun initially for protection as a woman travelling alone and later because of Hogan's initial stated reluctance to protect her had she not been a nun. Although Hogan is shocked, resenting all the chaste nights they spent together travelling, he kisses her and declares it is a bad time to indulge. The two team up to infiltrate the fort and let a squad of revolutionaries in through a trapdoor, while two other squads attack the gates and a fourth acts as sharpshooters.
Expecting the French army to be drunk for Bastille Day, they instead find that the train's destruction has put the garrison on high alert. Hogan and Sara infiltrate the fortress by Hogan posing as a bounty hunter, who has captured Sara and is turning her in for the reward. The ruse works, and Hogan and Sara engage the French commanding officers while the garrison's gates are breached for the Mexican revolutionaries to swarm through. A battle ensues, the French are defeated, and the Mexicans capture the fort. As promised, Hogan receives half the riches. Now wealthy and with his job completed, Hogan sets off with Sara, now wearing a garish red silk gown and feathers instead of the habit, the romantic couple now intending to open a gambling house in San Francisco.
