In the spoiler-sensitive environment of today’s entertainment, there may be people who resent the opening scenes of Annihilation, which gives away most of the movie’s direction. A biologist named Lena (Natalie Portman) has survived a cataclysmic event. Sitting in an isolation chamber, surrounded by unnerved people in hazmat suits, she’s interrogated about what just happened to her. In the process, she reveals who among the yet-to-be-introduced cast of characters survives, and who dies. And the scene makes it clear that while some of her companions may be alive, she’s the only one who made it back to report. This framing device can’t quite be called foreshadowing: the details Lena lays out are too solid to be shadows. They’re just fore-facts. And they hang over Annihilation with a sense of leaden inevitability.

But it’s a mark of success for the film that even knowing the outcome doesn’t disperse the tension. Annihilation is a portentous movie, and a cerebral one. It’s gorgeous and immersive, but distancing. It’s exciting more in its sheer ambition and its distinctiveness than in its actual action. And by giving away so many details about the ending up front, writer-director Alex Garland (Ex Machina) seems to be emphasizing that Annihilation isn’t about who-will-live dynamics, or the fast mechanics of action scenes. It’s about the slow, subdued journey Lena and the others take into the unknown, and how it affects them emotionally.

Throughout the film, which loosely adapts the first book in a trilogy by Jeff VanderMeer, Garland returns to Lena’s after-action reports to add some insight into what she was feeling and thinking during her experience. But framing aside, he opens with Lena mourning her husband Kane (Oscar Isaac, who also starred in Ex Machina), who disappeared a year ago on a covert military mission. Lena is a seven-year Army vet herself, and her current career as a Johns Hopkins biologist doesn’t provide any hint of how tough and ruthless she can be in a combat situation. But when circumstances lead her to join a team investigating an eerie phenomenon known as The Shimmer, she straps her rucksack on and picks up a rifle like she never put it down.

The Shimmer started at the site of a meteor impact and has been slowly growing, engulfing a patch of land in an energy field that looks like a pulsing oil slick wiped over the air. Multiple teams of investigators and soldiers have been dispatched into the area over the past year, and none have reported back or returned. It’s a compelling mystery, and potentially even an exciting challenge to the right kind of person.

But Garland is more interested in using The Shimmer to explore the human urge toward self-destruction. Since all-male Army squads have failed to conquer the region, Lena’s team of explorers represent a new tactic: they’re all women. Psychologist Dr. Ventress (Jennifer Jason Leigh), physicist Josie (Tessa Thompson), scientist Cass (Tuva Novotny), and paramedic Anya (Gina Rodriguez) barely comment on the gender choice. But the personal mix is another matter. As Cass points out, each of the women has some reason for self-hatred and guilt, which might explain what they’re doing on a possible suicide mission. In a more literal, spelled-out screenplay, their specific reasons for anguish might play out in obviously appropriate ways, and lead to their specific ends. But Garland uses the women’s backstories more abstractly, to illustrate what might push people to venture deeper and deeper into eerie, dangerous territory, against all common sense.

There certainly are surprises in Annihilation’s slow, creepy march toward the sole-survivor situation laid out in the opening scene. Some even come through conventional action sequences. But mostly, Garland builds up the uncanniness and the dread factor of the world inside The Shimmer. There are specific principles at work in the phenomena Lena’s troop finds, but they unfold in a variety of quietly unsettling ways, suggesting a wide range of potential ugly deaths ahead. Annihilation follows the familiar form of science fiction horror found in films from Alien to The Cloverfield Paradox, with a cast of characters in isolation, slowly being picked off by a force they don’t understand. But Garland’s film more closely resembles Denis Villeneuve’s recent science fiction hit Arrival, another slow, airless, fascinating film pocked with moments of sudden explosive action. Like Arrival (or Ex Machina, for that matter), Annihilation is a thoughtful, philosophical movie, more interested in the nature of humanity and the urges that drive us rather than in who lives or dies.

Garland’s film owes a lot more to an older movie, though: Andrei Tarkovsky’s 1979 Russian masterpiece Stalker, also about a group of people who set out on an expedition toward the center of an alien region, where their internal struggles manifest as part of a grand metaphor about the human condition. Like Annihilation, Stalker is a heady, cerebral movie about the baggage people carry, and how it might manifest in a surreal setting that reflects people’s interior lives in unpredictable ways. The plot parallels are significant, but Garland’s use of oppressive atmosphere and some of his specific visuals toward the end are even more telling. And so are his specific preoccupations in the script, about memory and perception, and about what separates people from their environment and each other.

Stalker wasn’t particularly well-received on first release — The New York Times’ Janet Maslin focused almost entirely on dismissing its “stupefyingly drab and slow” pace, and other contemporaneous reviews focused largely on its stunning visuals. Like so many clearly avant-garde films, it wasn’t recognized as a classic until much later. Annihilation seems destined to walk the same path. It’s nothing like a safely commercial film: like Ex Machina, it asks viewers to be patient with its mysteries, and with the relatively subtle emotional responses of a group of characters who are all clearly repressing their fear and frustration, right up until the moments where they explode. Like Arrival, it’s starkly beautiful, with an increasing emphasis on the alien aspects of its environments as the story goes forward. Toward the end, Garland brings in trippy visual elements from 2001: A Space Odyssey, and the kind of puzzle-ending that seems destined to send viewers running to friends and the internet to unpack clues and spin theories. But only the most patient, receptive viewers are likely to find the film satisfying. This isn’t passive entertainment: it requires intellectual engagement with the themes, and a real interest in Garland’s ideas.

The one element in Annihilation that feels accessible and mainstream is the cast. Portman and Isaac have an easy, appealing chemistry in the flashbacks to their time together as a couple, especially in a winning bedroom scene where Lena aggressively laughs off Kane’s attempts to sentimentalize their relationship. That sequence alone marks her as a bit of an iconoclast, a woman with strong opinions and a quirky, unusual, but well-expressed sense of humor. Leigh makes Dr. Ventress similarly fascinating, playing her with a dismissive drawl that’s equal parts pained and hurtful to the other characters. And Tessa Thompson, Thor: Ragnarok’s swaggering Valkyrie, displays a more vulnerable side here as the group’s least militarily adept warrior.

But all of the cast dial their emotions down as the story plays out, and they rapidly stop being distinctive characters and become illustrations of the themes instead. Their solemnity and the way they internalize their reactions keep Annihilation from being any sort of conventional horror story, where overt terror is usually central to the story. Instead, the dialed-down performances contribute to the feeling that this film is primarily a cold intellectual exercise. It’s not about flashy, colorful forms of self-destruction, but about the subconscious urge to take control of the slow march to the grave by making choices that move it along faster.

In spite of the few films it mirrors and refracts, Annihilation feels nearly unique in that regard. Its thrills are mostly reflective and analytical. And there’s nothing wrong with that, as long as viewers are prepared to open their minds and engage their brains. For a genre that’s supposed to be about carefully considering the possibilities of the future, science fiction too often feels just as slick and mindless a genre as any other. Annihilation fights that trend, and makes its audiences walk away with a lot to think about.