Lucy Warburton, the mayor, and Kevin Garvey, the police chief, on the series premiere of “The Leftovers.” (Paul Schiraldi Photography/HBO Warner Brothers)

HBO’s new series “The Leftovers,” as you may have heard, is quite the bleak drama. The premiere picks up three years after 2 percent of the world’s population  140 million people  evaporated into thin air for no rhyme or reason. The show begins to deftly illustrate the many ways the horrifying event affects the citizens of Mapleton, a small town in New York. In short, no one is doing very well.

The disturbing opening scene (a brief flashback to the day it all happened, when certain people are just suddenly gone) makes it very clear: Even if you didn’t personally know anyone who disappeared on Oct. 14, the day of the “Sudden Departure,” the idea of such a freakish incident will really mess with your head. It could cause you to join a cult; start shooting random animals on the street; mix with the bad crowd at school; run through the streets naked because of a mental breakdown; or just develop a drinking problem.

[Related: ‘The Leftovers’ review: A biblical event leaves a sorrowful mystery]

The characters don’t talk a lot about about the confusion surrounding the Sudden Departure, so the audience has to fill in the blanks. We get a lot of info thanks to televisions in the background of multiple scenes, all turned to cable news. For example, we learn that Congress tasked a committee to figure out exactly why everyone disappeared. Was it the rapture? Something scientific? A miracle? (“If it was a miracle, I’m fairly certain, sir, that God sat this one out,” one man says.) The official word from the committee: After years of research, they have absolutely no idea what happened. Congress is not pleased.

Every talking head feels differently about the reasons behind Oct. 14. Some are certain it was something religious, while others believe it was simply a random incident. There’s one thing for sure: No one knows why Gary Busey was involved. We see on a cable news special paying tribute to the celebrities who disappeared, which includes the pope, but also Busey. So maybe it wasn’t the rapture after all?

Anyway, Sunday’s episode covered a lot of ground. Here’s how the main characters are grappling with the Sudden Departure so far.

Kevin Garvey

Kevin’s the police chief, and he’s got a lot of problems  not including his impressive abs, which he shows off in multiple scenes. First and foremost, his wife, Laurie, took off to join the Guilty Remnant, a creepy group that wears all white, smokes cigarettes all day and has taken a weird vow of silence. Their primary job seems to be stalking the citizens of Mapleton as constant reminders that even though things have sort of returned to normal three years later, no one should ever for a second forget about the horrible thing that happened. Though we don’t know until the end of the episode that Laurie is Kevin’s wife (he shows up, begging to talk to her, but gets in a fight with a guard and is turned away), we do know that he despises the G.R. and everything they stand for.

Kevin’s issues also extend to his kids. His daughter, Jill, is obviously traumatized by the loss of her mother to the Guilty Remnant. His son, Tom, has fallen in with a cult leader named Holy Wayne, who mysteriously heals depressed people. “You’re doing your best,” Jill’s friend, Aimee, tells Kevin after the three share an awkward home-cooked meal. That doesn’t entirely appear to be the case (as Kevin barely knows how to talk to his daughter anymore) but at least Aimee confirms that Kevin cooks a mean meatloaf.

Meanwhile, Kevin spends the entire episode in a state of anger at the world, but more specifically at the mayor of the town, Lucy. She insists on throwing a parade for Heroes Day, which the government is calling the third anniversary of the disappearance to honor those who are gone. No one seems thrilled with the plan, as one man at the planning meeting objects to calling the people who disappeared “heroes”  after all, his brother-in-law is gone, and he was a jerk.

“They’re heroes because no one’s going to come to a parade on ‘We Don’t Know What the [Expletive] Happened Day,'” Lucy responds flatly.

But Kevin thinks the parade is a bad idea mostly because he’s sure the Guilty Remnant is going to show up and ruin everything.  “They’re going to come tomorrow, and when they do, someone’s going to get hurt,” he snarls. (They do; more on that later.) Kevin’s warnings go ignored, though.

Though his family and frustrating work situation might explain why he’s constantly in such a horrible mood, we also get glimpses of a couple odd flashbacks. One is a naked man running through the woods that seems to be Kevin’s father, the former police chief who apparently went crazy. Kevin also has multiple disturbing run-ins with animals (as The Post’s Hank Stuever notes in his review, co-creator Damon Lindelof of “Lost” is all about the animal metaphors). He encounters a wild dog, which is shot in the head by an angry gun-toting guy; later, he sees a deer that is ripped apart by a pack of dogs, and he has no choice but to start shooting at all of them.

Laurie Garvey

No word yet on why Laurie abandoned her entire family to go live with the Guilty Remnant, but her life seems pretty grim. First, there’s the all-white clothing thing, and the outfits always look dirty because people are always punching the G.R. members in the face and knocking them to the ground. Then, it seems that their entire days involve “sustenance” (apparently a bucket of oatmeal or slop) and “watching,” just following around members of the town while smoking and not saying a word.

We can only guess that Laurie misses her family, judging by the look on her face when Kevin shows up to talk to her. But the G.R. house leader, Patti, holds up a piece of paper that says, “You Are Not Welcome  Here,” and underlines it for emphasis, so Kevin eventually takes off. Also, Laurie specifically asks to be assigned to the Heroes Day Parade, possibly for more of an excuse to see Kevin than what the G.R. decides to do at the parade. That’s right, even though it’s a day of mourning loved ones (the keynote speech is a woman whose entire family disappeared), the G.R. still has a message, holding up a sign of their own: “You’re Wasting Your Breath.” That leads to a massive fight that Kevin predicted, as the parade ends in chaos.

Laurie doesn’t get a lot of time on screen yet  probably because she can’t talk  but her storyline is about to take a turn. A young bride-to-be, Meg, shows up at the G.R. compound in the last few minutes, asking if she can stay there for a few nights. Some of the G.R. had been following Meg and her fiance for days, and it looks like their stalking may have been a recruiting method. Patti assures Meg she can stay with the G.R. as long as she likes and that Laurie will take her under her wing.

“Meg,” said Patti, who broke the vow of silence to welcome their new member. “You and I won’t speak again.”

Jill Garvey

Kevin and Laurie’s high school daughter is having a rough time of it, which makes sense, given that her mother left to join the cult and her dad has become an absentee parent. She’s trying to halfheartedly go through the motions of teenage life: Pay attention in class, play field hockey, go to wild parties and play an iPhone spin-the-bottle game with options that include “hug,” “choke” and “[have sex with another person in the circle].”

But none of those things are going great: She ditches class with her troublemaker friend, Aimee, to get high; she bashes in another girl’s nose during field hockey practice; and she leaves the party when she’s paired up with a random guy during the game. She runs into a pair of twin guys who seem like they could be her friends, and they all have a bonding moment when they discover a dead dog (the one Kevin shot and tried to return to its owner) in her dad’s car at the party, and bury it together.

Mostly, though, Jill just desperately seems to miss her mom. At one point, Kevin angrily punches a family photo that shows the four of them smiling in their younger days. Later on, Jill takes the picture and gingerly removes the glass, looking almost happy for the first time as she remembers being together as a family. It’s actually pretty heartbreaking.

Tom Garvey

The Garvey with the least amount of screen time (and who keeps screening his father’s phone calls), Tom has dropped out of college (for an upsetting reason that we do not yet know)  to join the cult of Holy Wayne, a guy who “heals” people of their burdens. That includes Rep. Witten, a congressman played by Buddy Garrity from “Friday Night Lights,” who has a lot of problems post-Departure and hopes Holy Wayne can help. After confiscating Witten’s phone and receiving a thick envelope of cash, Tom blindfolds the congressman and takes him to Holy Wayne.

While Witten and Wayne have their meeting, Tom heads out to the pool and starts chatting with Christine, a young girl who lives on the compound. Now, for those of us who have read the books, we know exactly what Christine is doing there and why, and wow, is it creepy. However, no spoilers here  all we see in the episode later on is Wayne meeting with Tom and threatening him to stay away from Christine.

And while the Garveys are the center of “The Leftovers” universe, there are lots of stories to tell about the citizens of Mapleton. We only get brief glimpses of some of them, including Matt, the guy distributing a newsletter with awful stories about the people who disappeared (trying to prove they weren’t special), and Nora, the woman whose husband and two young children were taken away by the Sudden Departure. It’s all a very weird, sad world, and we know it gets only more twisted from there.