“A good horror movie is in many ways like a good joke: Revisit the punch line too many times, and it wears out.” —Stephen King, “What’s Scary”

Poltergeist is a terrifying movie. Up until the final act, when protective patriarch Steve Freeling (Craig T. Nelson) starts screaming about Indian burial grounds, and skeletons begin popping out of the wet ground to menace him, the film doesn’t offer much explanation for what’s happening to the Freeling family. The theories on offer are disproved, or ultimately useless. The spirits in the Freelings’ home act like whimsical interior decorators in one scene, piling up chairs into geometric stacks, but before long, they’re convincing a parapsychologist that he’s tearing his own face into bloody gobbets, and stealing fragile 5-year-old Carol Anne Freeling into their realm. There’s no clear indication of what they want, and no clear limit to what they can do. Worst of all, there’s no obvious way to fight back, and the film mines constant terror out of the Freelings’ helplessness in the face of the threat.

But when the story continued four years later with Poltergeist II: The Other Side, a new set of filmmakers weighed down the shocks with backstory and lengthy explanations. They put a name, a history, and a set of disappointingly petty, mortal motivations on the monster stalking Carol Anne—the ghost of an evil preacher named Kane who betrayed his flock and left them to die in a cave under the Freelings’ house. The spirit world was no longer a vast mystery, but a physical place where the family could go en masse to stab Kane into permanent death with a magic Indian spear. Kane’s spirit followers still got up to unpredictable, dangerous weirdness, but their goals were clearer, and their methods more ridiculous. What was once an edge-of-the-seat, watch-through-your-fingers story became campy, ridiculous, overblown—and not particularly frightening.

That’s how horror franchises tend to go. An original idea or some genuine scares often get audiences’ attention, spawning positive word of mouth, and bringing in the ticket money. But as soon as a property makes serious cash, the pressure is on to crank out a sequel or six. The usual problems apply: More often than not, sequels are empty exercises in commercial greed, betraying any fresh ideas or unique elements their predecessors had. But with horror, those issues go much further, because horror sequels are literally the opposite of horror. Even the best of them fall prey to a few basic flaws:

1) Horror is about exploiting the fear of the unknown, but sequels are about capitalizing on the familiar.

At the root of every real scare is an unknown factor for the viewers: What was that noise? What is that thing, what does it want, and how do the characters kill it? Where is the axe murderer right now? Which of the people onscreen are going to die before the film is over, and how grotesque will it be when they do? The music indicates something intense is about to happen, but what? Many of these questions are repeatable in a sequel—jump-scares and harsh musical stings never run dry—but by the time the first movie ends, the biggest questions have been answered. Even if everyone in the film dies, the unknowns have been resolved. When viewers stumble out of the darkness of a theater and into the light of day, they’ve already answered the questions, “How bad will it get, and will I survive?”

No one goes into a horror movie seriously thinking they’re going to die, that Leatherface or the zombie horde or the Blob or whatever will jump off the screen and get them. But signing on for a really terrific scary movie—especially in a theater, where the experience is more enveloping, and it’s impossible to pause the story and walk away to defuse the moment—is like boarding a roller coaster. The experience is canned and planned, but in the immediate moment, the adrenaline and sense of peril feels real. And getting off at the end answers the questions “Was I ever in danger, or did I just feel like I was?” and “How bad can it get?” Watching a sequel is like getting back on the roller coaster for a few more go-rounds. There may still be adrenaline left, but the real sense of threat is gone. An unknown quantity has become a known one. A ride doesn’t get scarier the second time around.

There’s a lot more flexibility in a movie sequel than in a roller coaster, but it remains true that going back for another dose of the same story is never the same. A good horror movie makes the world feel like the familiar rules have been suspended, like literally anything could happen—to the characters, and by proxy, to the audience. But once the experience is over, that feeling fades, and never fully returns on repeated visits to the movie—or to later extensions of the story, which almost always build on previously established elements. (Halloween III and Troll 2 notwithstanding.) A first-time experience can’t be repeated. At best, the appeal is, “I liked that before, maybe I’ll like more of it.” Which is nowhere near the same experience as, “I don’t know what I’m getting into, but I’m willing to take the risk.”

2) Real dread comes from negative anticipation—knowing something will happen, and wanting it not to. Just going to a horror sequel implies positive anticipation.

In “What’s Scary,” the 2010 intro to 1981’s non-fiction horror overview Danse Macabre, Stephen King talks about how the moral ambiguity of the Nightmare On Elm Street movies bothers him: “In A Nightmare On Elm Street, Freddy Krueger is flat-out evil—no question about it. We hate him and fear him from the get-go, and why not? He’s a pedophile, a murderer, and a disfigured psycho from beyond the grave. But seven sequels later, he has become, grotesque but true, a kind of pal. By the time Freddy Vs. Jason rolled around in 2003, we were no longer expected to root for the nominal good guys (teenagers without an ounce of fat on them). What we were rooting for as the sequels plodded on and on was a high body count. These sequels are basically snuff movies.”

He has a point, but he seems to miss that the sequels also become comedies. In the same way people often laugh with relief after being frightened, horror sequels tend to rapidly morph into comedies, because just by showing up, audiences have proved that they’ve stopped fearing whatever’s going to happen next, and they’re looking forward to it instead. Watching Freddy giggle as he runs Breckin Meyer’s character Spencer through a lethal videogame in Freddy’s Dead: The Final Nightmare isn’t scary, but it isn’t meant to be. Spencer is a newcomer to the franchise, and a short-lived one. He has no weight or importance. He’s a nobody, while Freddy is a familiar figure who’s been with the audience since film one. The audience has no investment in Spencer’s survival. They do have an investment in Freddy—after all, they’ve shown up yet again to see what he’s up to this time.

The same can be said of Hellraiser’s Pinhead, Child Play’s Chucky, Friday The 13th’s Jason (especially in Jason X, which takes place in space and is openly a comedy), Warwick Davis’ Leprechaun, or even the Rube Goldberg deathtraps of the Final Destination series. As victims come and go, they become faceless and generic. Meanwhile, the villains endure and become iconic characters, secretly the heroes of their movies. Once viewers are cheering for a villain, or laughing along with him, they aren’t afraid of him anymore.

3) Original horror movies can be entirely about atmosphere or the unexpected. Sequels usually feel a need to explain, explain, explain.

The Poltergeist movies aren’t alone in filling in the blanks that didn’t feel empty the first time around. Past the first installment in a franchise, filmmakers usually look for something to spackle in the spaces between shocks, and often, that putty is mythology. The Saw movies, the Hellraiser movies, the Exorcist movies—they all try to spin a relatively simple idea into something that gets more elaborate and complicated with every installment. Michael Myers is not scarier with a family connection to one of his victims, in a story suddenly needlessly complicated by druidic rites. And baroque backstory is the realm of fantasy, not horror. Putting a taxonomy onto a creature, or defining the process that rules it, is a form of taking control of it and taming it. (Which is why The Ring is so frightening—much of the film is about learning to understand something monstrous and mysterious, then finding that understanding it isn’t a workable defense.) The more a sequel focuses on pinning down what made the first film scary, the less scary both the sequel and the original become.

There are other problems with horror sequels: When they don’t overexplain or build a mythology, they tend to take the first film as a template, and repeat it by rote. Freddy, Jason, and Michael Myers have all died forever so many times that there’s no meaning to the ending of any of their movies anymore, and watching the latter two mechanically pursue their prey over and over and over has wrung most of the sense of story out of their films. The once-clever Final Destination movies have become a joyless slog of watching random elements fall together to kill essentially indistinguishable teenagers. Repetition is another enemy of horror: There’s no unknown factor, no sense of worry, in a closed loop of elements that repeat over and over.

Horror sequels also often come with bigger budgets than the original films, which gives filmmakers a mandate to make things weirder and wilder—which is almost never scarier. Like the sequence in The Ring 2 where the protagonists are attacked by a herd of CGI deer. It’s a strange idea, and it’s meant to be so strange, so far from the real world, that it’s unnerving and uncanny. But turning deer into murder-monsters is also so silly that it derails the story, not to mention any sense of suspense. Poltergeist is content with turning normal suburban objects—a doll, a tree, a mirror—into threats, but Poltergeist 2 includes a lengthy sequence where Steve Freeling drinks tequila and swallows a possessed worm that takes over his mind, until he vomits it up as an immense, slimy monster that attacks him. Again, it’s too elaborately ridiculous to be scary. In Danse Macabre, King draws sharp lines between terror (the anticipation of something frightening about to happen), horror (the shock when it happens), and revulsion, which is a simple gross-out scare. There’s plenty of revulsion in the kinds of effects-laden, outsized antics that sequels often use to up the ante, but both terror and horror are diminished by any hint of ridiculousness, any escape valve from the sense of being alongside the characters and in the moment.

The horror sequels that do get it right usually make an end-run around the familiarity problem by rebooting the story, or moving it to a new genre, or going back to basics. Establishing a willingness to leave familiar territory can go a long way toward making an old horror new again. So does keeping the action small, intense, and believable—creating a world that viewers believe they could live in, and more importantly, die in.

So horror fans should keep this in mind: Series and franchises work on recognition and comfort, not on fear. Studios love movie franchises because they keep people coming back. Financially speaking, they’re considered the safest bets. And good horror isn’t about safety. It’s about a sense of tangible threat. It’s about wondering what’s under the bed—not knowing from long exposure what’s down there, and hoping it makes a few good wisecracks this time around. Every original horror film starts out as an unknown factor, a coaster that hasn’t been ridden, a dark little vial that could be full of juice or poison. Even the ones that turn out to be disappointing at least feel like risks at some point in the process. That’s where horror comes from—the unnerving but delicious anticipation that maybe this time the rules will get broken, and the unknown will fully, finally take hold of us all.