Diego de la Vega, an eighteen-year-old nobleman, returns to his Southern California homeland after studies in Spain. He finds San Tasco gripped by oppression under Commander Raymond and Lieutenant Gabriel, who enforce unjust taxes and brutal treatment. Witnessing this tyranny, Diego adopts the secret identity of Zorro—a masked vigilante combating corruption and defending the vulnerable. To conceal his dual life, Diego meticulously crafts a public persona of clumsiness, laziness, and cowardice. This facade confuses his adoptive brother Bernard and disappoints his childhood friend Lolita Prideaux, both recalling his once-spirited nature. As Diego, he avoids confrontation and feigns disinterest in physical skill, starkly opposing Zorro’s fearless heroism.

Operating nocturnally, Zorro employs masterful swordsmanship to disrupt military schemes, marking each intervention with a carved "Z" from his rapier. His horse, Viento, ensures swift escapes. Bernard uncovers Diego’s secret and becomes "Little Zorro," aiding missions as an intelligence-gathering sidekick. Diego’s relationship with Lolita grows intricate: she openly derides his apparent weakness while unknowingly developing affection for Zorro. Diego maintains calm rationality in both roles, contrasting Lolita’s and Bernard’s impulsivity. His father, Don Alejandro Vega, remains unaware of the secret, though Diego wrestles with guilt when deception strains their bond.

Physically, Diego’s brown hair, blue-gray eyes, and slender build serve both identities. As a nobleman, he wears refined civilian attire—typically a white shirt and dark vest. As Zorro, he dons all-black garb: a face-concealing mask, cape, wide-brimmed hat, and knee-high boots. Diego’s actions consistently prioritize justice: shielding the oppressed, dismantling corruption, and preserving his secret to protect loved ones. He strategically leverages intellectual cunning as Diego and physical prowess as Zorro to restore fairness in San Tasco.