Anita, a Mexican girl, falls in love with John Gordon, an American mine superintendent hated by her brother Pedro. Pedro plans Gordon's assassination. Anita conceals in her clothing a black bean, and feigning that Gordon has done her wrong, goes to her brother and begs to be allowed to kill the American. As she has expected, Pedro tells her that the assassin will be chosen by lot, and then he passes round a hat full of beans, all of which are white save one, which is black. Anita surreptitiously takes the black bean out of her waist and the duty of planting the bomb which is to destroy her lover is accorded to her. After she disguises herself as a man and rides off, Pedro discovers the black bean left in the hat. Suspicious of Anita, he follows her on horseback. She does her best to evade him, but is caught and forced to plant the bomb, but she has secretly removed the fuse. Meanwhile Gordon finds the unexploded bomb, and looking for its thrower, he sees Anita struggling with Pedro in the distance. Gordon arrives just in time to save the girl's life, and the brother and his horse, falling over the cliff, are killed.
—Moving Picture World synopsis