The ending of Annihilation explained

Alex Garland's Annihilation is finally here. It's based on the novel of the same name by Jeff VanderMeer and tells the story of a group of scientists venturing into a strange quarantined zone called the Shimmer. Inside, they encounter monsters, an alien, and the key to humankind's potential destruction or salvation. The film juggles some heavy themes and has a lot going on in its narrative, so, by the time it ends, it's a little difficult to unpack. Luckily we're here to break down the ending of Annihilation for you.

Lena's affair

In the trailer for Annihilation, we find out in passing that Kane, the husband of Natalie Portman's Lena, leaves for an undisclosed mission (which turns out to be his excursion into the Shimmer) a day early. It's glossed over in the trailer as a moment of little significance, really serving more as a quick snapshot of the couple's apparently loving relationship. It turns out there's far more to it than meets the eye.

Lena and Kane's seemingly perfect relationship is slowly revealed to be a sham as the film goes on. It turns out, Lena's been having an affair with a colleague from work in the time leading up to Kane's mission into the Shimmer. As Lena observes at one point, Kane has probably figured out this is happening. As a result, Kane leaves for his mission a day early, his exit ringing as curt, almost cold. Kane proceeds to go into the Shimmer with something of a self-destructive streak growing in him — a theme heavily explored in the rest of the cast as the movie proceeds.

The Shimmer is an alien force

The film's primary question from the get-go is "What is the Shimmer?" Answers are alluded to however in the film's opening shots, which show some sort of interstellar object careening through Earth's atmosphere and crashing into a lighthouse. That lighthouse is both the focus and the destination for the excursions into the Shimmer organized by the military and researchers in Area X (the land surrounding the Shimmer). While by now we know the shimmer comes from space, we don't actually know what it is.

The Shimmer, as it turns out, is some sort of alien force. It's sentient — a living, breathing thing that is ultimately tied to an alien being that we see take on humanoid form in the film's closing moments. Everything in the Shimmer seems to be a part of this one creature, so, when that creature dies, the Shimmer fades away.

The Shimmer functions as a genetic prism

Annihilation's secondary focus comes down to not what the Shimmer is but what the Shimmer does. Determining this is the primary goal of Lena's team, made up of scientists working in various fields. Until Kane, nobody who entered the Shimmer ever returned (and he himself seems to be sick, no longer fully in control of himself — clearly in pain, under some sort of control of the Shimmer), so the Area X crew can't say for sure what happens in the Shimmer. As Lena and her crew journey in, they begin to realize what it is the Shimmer does.

The Shimmer isn't an explicitly destructive force, as it at first seems to be. The land inside is no ravaged wasteland but rather a lush, exotic forest filled with surreal flora and fauna and animals that only vaguely resemble those we see on Earth. The scientists discover that everything exposed to the Shimmer is in a constant, accelerated state of mutation. Everything is constantly evolving, growing, and changing. What's more, that change and mutation isn't confined to singular DNA sets. 

Scientist Josie (played by Tessa Thompson) is the one that realizes that the Shimmer refracts DNA the way a prism refracts light. This means that mutations amongst DNA spread throughout the environment, creating crossbreeds between humans, animals, and plants — a sort of "species blend," such as the alligator with shark teeth or the bear crying like a human when it means to roar. By refracting DNA, the Shimmer creates a world in which everything is interconnected on a biologic, genetic level.

It could destroy humanity

It's established early on in the film that the Shimmer is spreading. As the scientists journey deeper into its confines, we see a base that initially served as Area X's headquarters has now been completely overtaken by the Shimmer. Its threat is made abundantly clear by Doctor Ventress (Jennifer Jason Leigh): If it goes unchecked, the Shimmer will consume the world. Based on what we see inside it, that won't bode well for humanity as we know it.

The Shimmer is, literally, littered with corpses, mutations, the bones of those who have ventured into it in the past. Amidst its natural beauty lies an overwhelming sense of dread. The Shimmer will mark the end of humanity as we recognize it. Humans in the Shimmer encounter violent ends, like Anya's death at the hands (paws?) of a mutant bear or a sort of transcendent, gruesome absorption like that experienced by Doctor Ventress. That's not even getting into the madness it seems to instill in humans as their bodies and minds begin to mutate and blend with surrounding DNA. The film never makes a statement on whether this is a good or bad thing. It simply presents it as an inevitability.

Humanity's end could be a good thing

While Annihilation never explicitly takes a position on whether or not what the Shimmer does is ultimately good or bad for humanity, it does present the viewer with the idea that one can make of it what they wish. Early on in the film, we see two members of Lena's team die brutal, painful deaths by way of mutilation. One of them, Sheppard, is absorbed into the bear and becomes a part of its mutation in the moments of her death. The result is a gruesome, monstrous creature that echoes her final cries of "Help me!" whenever it speaks. This proves a turning point for Thompson's Josie, who takes matters into her own hands the following day.

In one of the more poignant moments of the film, Josie allows herself to willingly join the flora and fauna that have mutated into her DNA. Early on in the film, it's mentioned that she's a recovered self-harmer and may or may not have survived a suicide attempt. Josie saw what happened to Sheppard in her final moments and refuses to let that be the way she dies. It doesn't even seem like death, really. Rather, Josie transcends and becomes a part of something beautiful. In this, the film argues that humanity's fall is only violent if we make it so.

Lena finds the alien

Toward the film's climax, Lena encounters Doctor Ventress, who has finally accomplished her goal of making it to the Lighthouse. However, Ventress has transformed, become a part of the alien force that created the Shimmer, and she soon transcends her human form and becomes a sort of fractal prism herself. After this prism absorbs a drop of Lena's blood, it takes on a humanoid form. In this moment, Lena effectively meets the Shimmer.

While it initially seems malicious, the Shimmer never actually sets out to harm Lena. Instead, it mirrors her movements, mimicking her every step and motion, albeit on a slight delay. It's an important moment that embodies the goals of the Shimmer — it seeks understanding and integration. This becomes more evident in the film's closing moments (more on that later), but this is where we first begin to really understand what it is the Shimmer does. It assimilates to its environment, with the mass mutations and prism effect being the result of said assimilation.

Lena destroys the Shimmer

As her confrontation with the Shimmer creature comes to a head, Lena utilizes a phosphorus grenade to take it out. The Shimmer, a portion of it now in a humanoid form and morphing into Lena, is given the grenade by the real Lena: She places it in the Shimmer's hands, pulls the pin, and runs. As the grenade explodes, the Shimmer creature catches aflame; the lighthouse burns, destroying the entirety of the Shimmer with it. While this cements the fact that the Shimmer was one large collective being, it also allows Lena the opportunity to escape and make her way back to Area X. 

Back at the base, the Shimmer's hold over Kane now seems to be broken. Ultimately, this is the resolution to the film's primary narrative. The group's mission has been fulfilled by Lena. The Shimmer is gone … Or is it?

Everyone is inherently self-destructive

Annihilation is a movie about destruction, about the idea that deep in our genetic coding there is a primal urge to ruin, to destroy ourselves and the world around us. No matter how perfect our lives may seem, we will find a way to lay waste to them. It is our way. This is the Shimmer. The Shimmer serves as an embodiment of that urge, of that inevitability. It destroys what we have and turns it into something new, sometimes better and sometimes worse. The penchant for self-destruction is explored intensely through our protagonists.

Lena is a woman who ruins her marriage with an affair and then indirectly sends her husband on a suicide mission. Alma is a recovering addict. Josie is a former self-harmer. Ventress is dying, her cancer a physical manifestation of her fascination with the Shimmer. These characters have a subconscious death wish as it is, so their journey into the Shimmer seems inevitable, as does their end. Even though Lena survives, she only does so by killing a doppelgänger of herself, effectively wiping away her identity and emerging as something new.

Lena is released from quarantine

The film is nonlinear, with occasional segments focusing on Lena in the wake of her Shimmer endeavor. After emerging from the Shimmer, she's forced to take part in an extensive debriefing about her journey there while under a strict quarantine — the man conducting the interview does so in a hazmat suit. There's a fleeting moment where we're not sure if she's going to be another double created by the Shimmer, but this is quickly disproven. It's the real Lena.

Lena's eventually reunited with Kane, who's no longer dying from the Shimmer's effects and even seems lucid. It's about as close to a happy ending as we get from a film so inherently grim as Annihilation, so we'll go with it.

The Shimmer lives on

The most ambiguous moment of the film takes place in its closing moments: Lena has known since encountering a video recording by her husband at the Lighthouse that whatever is back in the Area X facility that has taken his form isn't him. She knows something is amiss. Nobody else at Area X knows this, and she clearly doesn't disclose her inside information to anyone else at the facility. As such, her being reunited with Kane isn't quite the moment those around her believe it is. They think she's being reunited with her husband. She knows the truth — namely, that she needs to tie up this last loose end.

Lena asks this doppelgänger if he (it) is really her husband, to which it responds, "I don't think so." It's clear: Kane isn't Kane anymore, he's the last remaining fragment of the Shimmer, whether he fully knows this or not. 

In the film's haunting finale the two embrace as both of their irises fluctuate and change color, dictating the continuing mutation and evolution caused by the Shimmer. It now resides in Lena and Kane, who will live on to change the world even further. It might not happen now. It might not happen tomorrow. But the primal coding that sends us toward self-destruction and evolution still remains as a perpetual inevitability that we will never fully escape.