While hiding out in Mexico Gabriel Moonlight is confronted by Ellen Kincaide, a novice nun who begs him to revenge the death of her sister and Gabriel's former girlfriend, Cally. He refuses to help, knowing if he returns to New Mexico he will be hung for his crimes as the outlaw Mesquite Jennings.Later, Gabriel learns Ellen has been kidnapped by bandits and now sets out to rescue her. With a change of heart he also promises to kill the man who murdered Cally. But when he discovers the identity of the murderer Gabriel knows that to exact retribution means almost certain death. Even so, a promise is a promise.