Don Diego Dela Vega has been studying in Spain for three years, and returns to California in 1820 as a master swordsman. Upon learning that a new Commandante has taken command of the Los Angeles pueblo and rules with an iron hand, Diego pretends to be a man of books and music, eschewing violence. With the help of his mute man-servant, Bernardo, and a black stallion named Tornado, Diego dresses all in black and rides into the night to free a wrongly imprisoned landowner. Hiding behind a mask to conceal his identity, he calls himself Zorro and tangles with Captain ...
Don Diego shows his man-servant, Bernardo, the secret passage in his father's hacienda that leads from his bedroom to the stable below, where he keeps the black stallion, Tornado. Captain Monastario posts a reward for the capture of Zorro, and begins visiting the local haciendas in an effort to discover who Zorro might be. When he arrests the wrong man, Zorro must ride again to prove to Monastario that he has the wrong man.
Capt. Monastario dispatches Sgt. Garcia to delay the arrival of Judge Vasca to Los Angeles, until the Capt. can insure a guilty verdict in the trial of Nacho Torres. Zorro must thwart Monastario's scheme.
Capt. Monastario and Sgt. Garcia hatch a plan to capture Zorro. Sgt. Garcia pretends to be dishonorably discharged from the military, letting it be known he wants revenge, in hopes of drawing near to Zorro.
After witnessing a stranger's fencing skills, Capt. Monastario plans to discredit Zorro by disguising the stranger as Zorro, and have him rob the rich landowners during a social gathering--but the real Zorro arrives on the scene.
Capt. Monastario arrests Don Diego for being Zorro, and plans to present him to a visiting dignitary, Viceroy Don Esteban. Don Diego manages to outsmart Capt. Monastario, and he is relieved of command.
With Capt. Monastario gone, Don Diego believes Zorro's job is now finished, never to ride again. But when the new Commandante arrives in the pueblo, he is promptly assassinated by Esteban Rojas, a member of a secret society of villains using eagle feathers as their call sign. Maria Crespo, a barmaid in the tavern, witnesses Rojas fleeing the crime scene, so he takes her captive and plans to eliminate her. Zorro must rescue her.
Magistrado Galindo arrests a peasant on phony charges of civil unrest, and sentences him to be executed at midnight. He stations the soldiers around the plaza so as to capture Zorro if he attempts a rescue.
Carlos Urista inherits the family ranch, but loses it in a card game. Magistrado Galindo plans on taking control of the hacienda and controlling the water supply to all the other ranches. Zorro steps in to prevent it.
The Commandante sets a trap for Zorro by placing an imitation Zorro in the plaza, and waiting for the real Zorro to appear. Capturing Tornado they hold an auction, hoping to catch Zorro bidding on his horse.
Don Juan Ortega is still pretending to be the Commandante of the pueblo, and when he sees Rosarito Cortez, he attempts to kill her before she can identify him as an impostor. Zorro must intervene and save her.
A gypsy woman comes to the pueblo with a couple of golden nuggets, and a prospector sees them and kidnaps her. Forcing her to take him to where she found them, he discovers an Indian gold mine. Zorro must save her.
The new Commandante arrives in the pueblo, and appears to be an honest and just man. Realizing the Commandante is fiercely jealous of his wife, the Magistrado sends a 'Don Juan' to serenade her, but Zorro thwarts his plan.
Magistrado Galindo calls together a meeting of all the important landowners in the pueblo, and with his band of rogues he plans on framing the Commandante as an accomplice of Zorro, but the real Zorro shows up.
Here we first meet "The Eagle" - Jose Sebastian Varga, who sends two of his men into the pueblo with kegs containing a load of stolen gunpowder. Meanwhile, Commandante Toledano is sent to San Diego to investigate the theft of the gunpowder, but his wife Raquel stays behind in Los Angeles - and we learn that she too is working for The Eagle.
Raquel, Salvador and Enrique get Sgt. Garcia to imprison Don Diego on charges he is Zorro, in hopes that the real Zorro will come to his rescue, and be caught. Zorro must somehow escape from his jail cell.
Sgt. Garcia discovers that someone has stolen the pueblo's gunpowder, and replaced it with charcoal. Raquel, Enrique and Salvador plan to kill Sgt. Garcia, but Zorro tries to prevent it from happening.
Raquel Toladano expresses doubts concerning her involvement in the Eagle Feather Brotherhood, and is taken hostage by the other members as they prepare to move their stolen gunpowder. Zorro must stop them.
Carlos Murrieta arrives in Los Angeles, but when he makes advances on Maria Crespo, young Don Rodolfo becomes jealous and challenges him to a duel. Zorro intervenes, and discovers Murrieta is an agent of the Eagle Brotherhood.
Carlos Murietta hides his box of stolen jewels in Jose Mordante's blacksmith shop, but Bernardo discovers them. Mordante attempts to kill Bernardo and keep the jewels, but Zorro arrives to save Bernardo. The jewels are missing however.
Carlos Murrietta's brother, Pedro, arrives from South America with the second shipment of stolen jewels. Zorro searches the blacksmith's shop for the first shipment of jewels, and must tangle with both Murrietta brothers.
The new Magistrado, Jose Sabastian Varga, arrives in Los Angeles and immediately takes over Don Diego's hacienda. He plans to use it as his headquarters, but Don Diego and Bernardo suspect he works for The Eagle.
A European count arrives at the hacienda looking for the Eagle, not knowing that he has left to take new headquarters in the town. Investigating to find out what the count's business with the Eagle is, Diego and Bernardo discover that cannonballs are being brought into Varga's headquarters hidden inside art vases.
Believing Zorro to be dead, and with most of Garcia's men out of town, Varga decides to put his plan to take over all of California in motion. He imprisons Don Alejandro, Diego, Bernardo, and Garcia, and his men overwhelm what there is of Garcia's forces. All Varga needs is the list of names of the men in Don Alejandro's army. To stop the mad "Eagle", Diego must pretend to betray his father.