Sergeant Garcia returns from escorting Padre Simeon on a trip from San Diego and is surprised to find that almost everyone in Los Angeles has contracted the measles. The doctor has placed the entire pueblo under quarantine and restricted residents to their homes. Even the soldiers cannot leave the cuartel. The padre has brought a large gold chalice to Los Angeles for use in the mission and wants the town to know of its arrival. He asks Diego to take him through the pueblo so the people can see the religious symbol. Diego, who has already had the measles, agrees and helps the padre, who then takes the chalice home for safekeeping. The padre's servant, Carlos, is a former criminal, and the valuable chalice proves too much of a temptation for him. He locks the padre in a closet and takes the chalice, posting a quarantine warning on the door. If no one enters the house, the padre will die of thirst and hunger. Luckily, Diego comes to visit and realizes something is wrong when he sees the sign, for the padre was quite healthy the day before. The padre tells him of Carlos' actions and Diego rushes out to find the chalice. Dressed as Zorro, he tracks Carlos to a cabin where the thief is about to melt down the stolen relic. Zorro stops him just in time. Carlos tries to kill Zorro but is defeated. Zorro then sends him back to town to prove to the padre that he deserves another chance.
Elenco: Guy Williams , Gene Sheldon , Henry Calvin , Jolene Brand , Eugenia Paul , George J. Lewis , Guy Williams , Henry Calvin , Jolene Brand , King , Richard Anderson .