HBO's stunning sequel series wrestles with big questions about American identity without sacrificing big-scale entertainment.

Much of what “Watchmen” is about — and Damon Lindelof’s substantial adaptation of Alan Moore’s sprawling graphic novel is about quite a lot — can be summed up in a joke. Well, it’s not really a joke, but the cunning and cutting Jean Smart still sells it that way.

“You know how you can tell the difference between a masked cop and a vigilante?” Smart, as FBI Agent Laurie Blake, asks.

No-bullshit Tulsa police detective Angela Abar, played by Regina King, answers plainly, as expected: “No.”

“Me either,” Laurie says — and that’s the end of the joke.

Masks, identities, and the murky, muddled truth they form are central themes of “Watchmen.” If the cops and criminals wear masks, how do you tell them apart? Who’s the hero and who’s the villain? Who, in other words, do you trust? Looking beyond the veils people share with the world, “Watchmen” finds fundamental truths about an America divided by a lack of faith in itself, its people, and its institutions. The series’ scope is astonishing given its subject matter, and even more so given its relentless entertainment value. Through six episodes, “Watchmen” has already provided a bounty of intelligent theories to study and debate, but it’s designed to be one helluva good time, as well.

And it is. While it’s best to go into “Watchmen” sans spoilers, a bit of framing can be helpful in getting a grip on its hefty world-building. Everything that happened in Moore’s graphic novel is canon — the creation of Dr. Manhattan, winning the Vietnam War, even the Minutemen are all part of the past for everyone in the series. Certain events will be referenced, plenty of easter eggs are well-placed, and some established characters (like Laurie) play key roles in the new story, but you do not need to know the original comic by heart to appreciate this fresh creation from Lindelof and fellow executive producers Tom Spezialy (“The Leftovers”), Stephen Williams (who also directs), and Nicole Kassell (who helms the first two episodes).

HBO

The immaculate pilot, directed by Kassell with powerful fixed framings (reminiscent of the comic’s panels) and rich contrasting colors, sets up a conflict between local law enforcement and domestic terrorists. The Tulsa P.D. have negotiated a truce, of sorts, with a masked group known as the Seventh Kavalry — until an officer-involved shooting reopens old wounds.

In examining their conflict, “Watchmen” starts upending expectations and provoking conversation. Many of the targeted police officers, led by King’s character, are black. The Kalvary, who wear the mask of a former hero named Rorschach, is made up of white supremacists. This juxtaposition of a powerful black police force and a powerless white minority is purposeful, though not in obvious ways from the outset. The choice grows more effective and affecting as the series rolls on, as does much of the show’s more enigmatic scenes, set-ups, and subjects.

Lindelof has always enjoyed throwing his audience for a loop. Whether it’s an unexpected flashback, the sudden introduction of a new character, or starting a season by chronicling a pregnant cavewoman giving birth, the “Lost” and “Leftovers” showrunner tosses curveballs for the same reason a pitcher does: to keep the batter/viewer on their toes. But he also trusts his audience as much as he respects them. Seemingly random scenes always serve a purpose, if not multiple purposes, even if they can be overwhelming. At one point, a character says, “There’s a vast and insidious conspiracy at play, here in Tulsa. If I told you about it, your head would explode, so I have to give it to you in pieces” — that’s how it can feel watching “Watchmen”; as though your brain might snap from information overload. (Thank goodness HBO is still on a weekly rollout.)

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Still, it’s balanced — if you’re feeling overwhelmed, it’s easy to appreciate the endless easy pleasures offered by this exceptionally cool adaptation. Big, loud, and intense action scenes are captured in giant fields, where the choreography of each movement is played out like a badass ballet. The same goes for the convincing hand-to-hand fights, which make the most of an able cast. Speaking of, King is nothing short of amazing — yes, she’s got an Oscar and three Emmys, but she puts even more range on display in a turn that effortlessly pivots between invulnerable and vulnerable. Jeremy Irons is having a ball as Probably Who You Think He Is, while Smart, Tim Blake Nelson, and Don Johnson each make you fall for them all over again. And yes, the costumes are so damn good-looking Halloween 2019 is going to be overloaded with cops in yellow masks.

When Smart tells that joke, she isn’t wearing a mask. She’s with the FBI, so she doesn’t have to. In “Watchmen’s” alternate reality, only local police are required to hide their identity. Anyone else who dons a disguise is considered a threat, in part because of Laurie’s past actions. Back in the ’80s, Laurie ran around as Silk Spectre, one of the many “heroes” who were either outlawed or privatized for government use after the public grew suspicious of their intentions, powers, and purpose.

Now in HBO’s “Watchmen,” Laurie is staring at a new form of costumed justice, and that figure is staring right back. The past and present are looking at one another, and neither likes what they see. “Watchmen” asks how we move forward from there; how we evolve, how we coexist, how we trust one another again. There’s no easy answer, but you’ll be shocked at how rewarding the search can be while watching this “Watchmen.”

Grade: A

“Watchmen” premieres Sunday, October 20 at 9 p.m. ET on HBO.

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