A group headed by a man known as El Lobo works for a profiteer named Marsden. Marsden is determined to gain control of the California Yucatan Railroad. El Lobo and his men continually sabotage the railroad project for Marsden in hopes that the railroad will be sold to Marsden.

Fortunately, the bomb misses the train. Zorro uses a rifle to shoot at the plane, and the damaged plane heads back to headquarters. Joyce and Philip notice that Zorro rides El Rey, the horse that ran away from James. When Marsden learns that El Lobo was not able to sabotage the payroll, Marsden tells El Lobo that most of the railroad's supplies are at Ocilla Junction. If the railroad loses the supplies, it will be forced into bankruptcy.

Zorro regains consciousness and jumps down into the cellar just as the bomb explodes. Zorro rides from Ocilla Junction with El Lobo and his men in hot pursuit, but Zorro gets away.

Zorro frees himself just before he would have been run over by the train. The train gets through the junction safely. El Lobo tells Marsden that the railroad has begun working once again. El Lobo learns of an important delivery of some deeds.

Renaldo appears in time to prevent Zorro's mask from being removed. The man who stole the deeds gives them to another man who delivers them to El Lobo. Two of El Lobo's men are captured by Zorro and turned over to the Rurales. Marsden tells El Lobo that they have got to get their man out of jail and that they have to get the deeds out of Mexico.

James escapes from the crashed plane with the deeds. Joyce finds the deeds at the mailbox, left by Zorro. El Lobo takes Philip and Joyce captive. El Lobo tells Joyce to deliver a message to Zorro, stating that Philip is a prisoner and will die unless Zorro surrenders.

Renaldo appears and prevents El Lobo from shooting Zorro. Zorro and El Lobo go to El Lobo's headquarters. Zorro finds a paper which proves that Marsden is behind the plot and reveals that El Lobo's real name is Brad Dace. Zorro brings the paper to Philip and Joyce.

Zorro tosses the box containing the important paper out the window and then hangs on to the window so that he doesn't fall when the floor collapses. Zorro jumps out the window, but one of El Lobo's men has already retrieved the paper and ridden off with it.

Zorro learns that El Lobo's men are going to blow up a tunnel. Zorro boards the train in an attempt to warn the engineer. The train travels through the tunnel, and as it exits, there is a large explosion.

The explosion causes some damage to the train and blocks the tunnel. Philip is badly injured and unable to work. Zorro takes Philip's place and helps get the tunnel reopened.

Zorro attempts to overtake the train in a truck. El Lobo and his men pull the records up out of the train car to the roof of the car. The truck races to catch up with the train. It appears that the truck and train will crash at the crossing.

Both the truck and the train stop at the crossing. El Lobo and his men surround Zorro. El Lobo pulls off Zorro's mask. El Lobo takes James and all of the railroad's records to his hideout. Marsden tells El Lobo to get James Vega's signature on a bill of sale for the railroad. El Lobo tells his men to bring Philip and Joyce to the hideout.