At the start of the first season of “Stranger Things,” the psychically gifted girl Eleven spells out the series’ central premise by flipping a Dungeons & Dragons game board and revealing her dark underside. A little boy is missing and the searchers have found nothing; Eleven says he is “hiding” in an evil alternate dimension that the show’s characters come to call the Upside Down. It’s a great scene for many reasons. There’s joy in the simplicity of the Upside Down idea and the directness with which it’s expressed. And the children, who are about twelve years old, are at the ideal age to accept such an idea. Seeing their eyes widen, your eyes widen too.

Four seasons later, the protagonists of “Stranger Things” aren’t jaded – they’re still surprised and appalled by what they see – but there’s a sense in which they’ve come out of their wonderful years. They are old enough to remember themselves younger and more impressionable. “‘The Neverending Story’—it scared me!” one of them remembers. The new season takes place in 1986 and “The NeverEnding Story” was released in 1984. Now in high school, they can look back nostalgically at the scary movies they watched in middle school. become experienced monster hunters, they can face the creatures that stalk them with aplomb on a daily basis. What really scares them are things like applying to college or saying “I love you” to a girlfriend. When the final season’s villain finally explains his desire to destroy the world, he argues that human society is cruel and oppressive – a “deeply unnatural structure” that is “dictated by made-up rules. Seconds, minutes, hours, days, weeks, months, years, decades – each life is a faded copy of the previous one. Waking up, eating, working, sleeping, reproducing and dying. Everybody just waits – waits for it all to be over, while playing in a stupid and terrible play, day after day. Adulthood, it seems, could be the real Upside Down.

The new season is long – eight episodes over an hour each, capped off by a two-and-a-half-hour finale – partly because it needs to pull the pre-teen version of the show into a more adult setting. It’s a labor-intensive process, which seems to require nearly every character to have a lengthy heart-to-heart conversation (“I see you”, “I’m here for you”, “I believe in you” , etc.) . But the overall effect is to raise the stakes of the series so that by the end of the season, it’s a team of adults facing potential disaster. (Stop reading if you want to avoid spoilers.) In the final episode, a giant portal to the Upside Down opens beneath Hawkins, Indiana, and the poisonous atmosphere of this lower realm flows out to the mundane world. . In one of the series’ best shots, Eleven walks through a field of vibrant wildflowers, then encounters a border beyond which the plants are newly dead and gray. She crosses to pick a wilted flower. It’s a chilling picture of permanent environmental degradation – an adult problem, far scarier than bogeymen from another dimension.

To some degree, all scary entertainment asks a serious question: what is evil? “Stranger Things” has always been a mashup of movies and books from the past. Season 4 combines elements of “It”, “The Matrix”, “Aliens”, “Pitch Black”, “Carrie”, “A Nightmare on Elm Street”. “, “Poltergeist II”, “Terminator 2”, etc., but the series also addressed this question of evil in a simple and refined way. In the show’s first three seasons, evil in the Upside Down tended to be gross, slippery, and otherworldly; she was Lovecraftian, in that she emanated from a twisted, morbid, and hidden part of nature. Science tells us bugs are beautiful and mold is gorgeous, but venture into a rotting basement or turn over a damp log and you might disagree. The Upside Down is a rotten world, and our horror stems from the realization that its decay is predatory, hunting us down even though we’re innocent.

Season 4 changes history. In the finale, a flashback to 1979 shows us a surprising and primordial Upside Down, a version that existed before the start of the series. It’s not a pleasant place – a small homuncular version of the show’s tulip-headed monster roams the rocks – but it’s also eerily pristine, as Earth might have been in a previous evolutionary time. Henry Creel, the villain, arrived there after killing everyone in the Psychic Experiment Lab under Hawkins. (After murdering his own family with telekinetic powers, he became the #1 subject in the research program that later produced Eleven.) When Eleven finds out what Creel has done, she is so filled with rage and in disgust she mindlessly opens the first crack between the dimensions and pushes him through her.

It was Creel, we learn, who made the Upside Down what it is. Initially messy, his powers were augmented under the traumatic tutelage of Martin Brenner, the scientist leading the Hawkins Project; once Creel finds himself in the Upside Down, he reshapes his raw materials in his image. “I know what he did to you,” Eleven tells Creel, of Brenner. “You were different, like me. And he hurt you. He got you into this. He’s the monster, Henry, not you. It’s a bit dubious: didn’t a young Creel, acting alone, use his powers to murder his mother and sister, framing his father for the crime? But the wider point is reasonable. Creel, in his demonic form – he now resembles the creature from the Black Lagoon and commands an army of monsters – wouldn’t have been possible if he hadn’t been twisted further by others. And that, in turn, means the Upside Down could have remained simply an unpleasant parallel world, rather than one that threatens to colonize our own.

This tale of evil is familiar and realistic. Disturbed people, encouraged and empowered, go on a rampage and commit unspeakable acts on a massive scale. (A warning card placed before the first episode of the season, in which many children are slaughtered, notes that viewers may find it disturbing “given the recent tragic school shooting in Texas.”) In some ways, this more grounded, human version of the Upside Down is actually scarier, as it embodies an evil for which we must take responsibility. But it’s also less supernatural, and therefore in some ways less disturbing. This shift from genuinely scary to merely psychological—from the unknowable to the explainable—is another way “Stranger Things” has become more adult.

Does it ever work to explain evil? For some of us, stories of why people do bad things can be satisfying. Piecing together a chain of events, leading from initial conditions to an end result, can make the horrible understandable. But, for others, there will always remain an element of the inexplicable. The demons in Upside Down turn out to be the product of a diseased human mind. But why are human minds sick? The alternate world that haunts ours was shaped by one person’s imagination. But why are people so ready to imagine such horrors? Is there a bloody vein connecting our present to our evolutionary past, or is the entropic and destructive aspect of the universe also woven into our nature?

In David Lynch’s “Twin Peaks” – the grown-up version of “Stranger Things” – evil remains elusive and elemental, and yet the realism of the terrible deeds the story revolves around remains uncompromising. The idea is that evil, even if it has to be faced, can never really be explained; even “adult” forms of evil, including ordinary heinous crimes, are haunted by something otherworldly, which makes them terrifying. Watching the new season of “Stranger Things,” you may feel that as we grow older, we understand better why the world is going wrong. But that too could be an illusion of youth. ♦