On the northwest coast of South America, a small colony of people has long been the target of masked bandit El Mocho and his gang. Francisco Suarez, whose father was murdered by El Mocho ten years before, has sworn revenge against the bandit and forms a band of "cabelleros," known as The Avengers, to protect the beleagured villagers. Suarez disguises his identity and assumes the name "Don Careless." Fearing for his future, El Mocho accepts the corrupt Col. Luis Corral's offer to fake his own death and be reborn as Lt. Hernandez, Corral's aide. The colony's governor, Don Rafael Moreno, has been taken in by the colonel and declared his intention to pass his authority onto Corral as soon as he marries the governor's daughter Maria. One night, at an inn, Don Careless encounters Corral as he is about to take unfair advantage of French colonist Andre LeBlanc in a sword fight. Don Careless saves Andre, who was angry over losing his estate to Corral in a gambling wager, then beats Corral in a close quarter duel. Although his defeat ruins his reputation as the colony's best swordsman, Corral decides that he can make use of Don Careless, who has boasted of his success as a ladies' man. Corral wants to marry his mistress, the Countess Yvonne, and assumes that even if Maria should turn him down in favor of Don Careless, the governor will still make him ruler. Corral bets Don Careless that if he can make Maria fall in love with him, Corral will return Andre's estate, but if he fails, he must become Corral's personal servant. As hoped, Don Careless wins Maria's heart, and is himself smitten by her. Eventually, his sense of honor gets the better of him, and he tells Corral that he has lost the bet. As Don Careless prepares to become Corral's servant, a jealous Yvonne informs Maria about the wager. Maria tells her father that she will never marry Corral, and though she still loves Don Careless, she denounces him. When Don Rafael refuses Corral his advancement, Corral orders El Mocho to resurrect his bandit gang and terrorize the colony. Corral forcibly seizes control of the government and kills Don Rafael. Maria and a repentant Yvonne escape, however, and return to Don Careless, who launches an attack against Corral. Don Careless and Andre succeed in overthrowing the Corral faction, and during the shooting, the colonel and El Mocho are killed. After Don Careless and Andre turn the government over to the proper authorities, Don Careless and Maria look forward to a happy future together.
