HBO’s “Watchmen,” in other words, is trying to analyze masked vigilantes through the prism of race and racial injustice. And while this has been evident from the beginning — the series opens with a harrowing dramatization of the 1921 Tulsa, Okla., massacre, in which a white mob destroyed the affluent black neighborhood of Greenwood, killing hundreds and displacing thousands — it has become even more apparent with Sunday night’s episode, titled “This Extraordinary Being.”

In it, we learn the origins of Hooded Justice, the first vigilante hero in the world of Watchmen. In the original comics, the identity of Hooded Justice is a mystery that goes unsolved. In HBO’s “Watchmen,” we’re treated to speculation in the form of “American Hero Story,” a show within a show. It depicts the in-universe past as a gritty, violent action series — a callback to and satire of Snyder’s “Watchmen,” which used the thematically rich source material as fodder for high-definition brutality. The Hooded Justice of “American Hero Story” is a powerful, hyperaggressive vigilante, clad in hood and noose and clearly — underneath it all — played by a white actor (Cheyenne Jackson).

But through an extended flashback, what we learn from this latest episode is that he was in fact a black man: a young New York City police officer in the late 1930s named Will Reeves (Jovan Adepo). We’ve already been introduced to an older version of Reeves. A survivor of the Tulsa massacre, he’s the grandfather (played by Louis Gossett Jr.) of the show’s protagonist, Angela Abar (Regina King). He’s also the prime suspect in the murder of Tulsa’s chief of police — the present-day event that sets off the show’s narrative.

After arresting a white man for setting fire to a Jewish deli, the young Reeves is beaten and nearly lynched by three white officers, who are leaders of the city’s Ku Klux Klan. As he walks away from the site of the attack — bloodied and draped in a hood and a noose — he sees a mugging. He could walk away. Instead, he acts. He fights off the attackers. The next morning, the local paper notes the altercation. Hooded Justice is born.

Practically impotent as a black police officer, Reeves has power to act while under the hood. But the mask doesn’t conceal everything — the skin around his eyes still marks him as black. And so he wears makeup and gloves to conceal his racial identity, to let the public believe that their hero is a white man.