I loved the movie: the visuals, the sound, the story pacing, the acting. It’s all there. What follows isn’t a review but a rather close synopsis of the plot as I plan to read the books and later compare the two.
Protagonist: Lena (Natalie Portman), an ex-Army soldier, cellular biology professor. Her Army husband Kane (Oscar Isaac) is missing for a year after having left for a secretive mission. Lena is devastated which is additionally worsened by her guilt for having a short-lived affair with her coworker Dan.
Kane suddenly returns but is confused about how he got back, where he got back from, communication with him appears very hard. He says to Lena strangely: “I was outside the room. The room with the bed. The door was open and I saw you. I recognized you. Your face.” He is clearly proud of this. This takes her aback.
His state soon deteriorates, she calls an ambulance but they’re taken to a secret facility instead. There Lena learns about The Shimmer, a coastal area in the southern US around a lighthouse hit with a meteor three years prior. The area is slowly expanding, missions to see what’s inside have so far all failed. Only Kane returned. He’s in intensive care. Lena joins four other women on another mission to find out what’s in the lighthouse.
The women are all “damaged goods”. The leader is psychologist Dr. Ventress (Jennifer Jason Leigh) who is terminally ill. Physicist Josie (Thesa Thompson) is suicidal. Geomorphologist Cass Sheppard (Tuva Novotny) lost her daughter to leukemia. Paramedic Anya (Gina Rodriguez) is a sober addict. Lena herself accepts the mission to fight the Shimmer as atonement for betraying her husband who likely took the suicide mission into the Shimmer because he found out about the affair.
After entering the Shimmer on foot, the women find themselves unable to communicate with the outside world due to all signals being scrambled, mixed. They are also confused about how much time has passed and have trouble remembering what happened since they walked into the Shimmer. The closer they get to the lighthouse, the group sees increasingly radical mutations of flora and fauna. Some of it is beautiful, some of it is scary. Mutated animals, different flowers growing from one plant, plants with human hox genes (the body plan, the physical structure). Josie realizes that the Shimmer acts like a prism: it mixes, mutates, scrambles everything. Light, electricity, magnetism, DNA.
Finally they reach a military base where Kane was stationed. They find video footage of Kane cutting somebody’s abdomen to reveal his intestines moving like snakes. The women find that soldier’s body, now turned into a colony of lichens. That same night a mutated bear drags Cass away. Lena later finds her body in the forest. In the mean time, Anya’s breaking down nervously since she observes her fingerprints changing. When she discovers that Kane is Lena’s husband (something that nobody shared with her), she gets all paranoid and ties up the other women at an abandoned house. She suspects Lena killed Cass as she did not see a bear and the body later. The bear reappears, luring Anya by emitting a cry for help in Cass’ voice. Anya tries to fight back but fails and dies. Josie shoots the bear.
Ventress leaves on her own to reach the lighthouse right away, being nervous that the Shimmer is disintegrating her body and she won’t be able to make it there and back before she’s destroyed. She’s right, Lena checked her blood the night before to discover her cells shimmering. In the morning Lena tries to convince Josie to move forward but Josie shows her that her forearms start growing leaves. She tells Lena that the bear cry suggests that parts of Cass’ consciousness was refracted onto the beast. Josie doesn’t want to face the lighthouse, she doesn’t want to fight it. But she also doesn’t want to be refracted onto something terrifying. Instead, she lets herself be refracted into plants of human form.
Lena leaves on her own and reaches the lighthouse. Inside, a video camera on a tripod shows Kane talking to the cameraman and committing suicide with a grenade. The cameraman turns out to be somebody that looks just like Kane. The one that returned from the Shimmer. There’s a meteor crater next to Kane’s blown body which Lena enters and hears Ventress. As she enters the chasm, she observes Ventress disintegrate into a form that absorbs a drop of Lena’s blood to become a shimmering humanoid that starts mimicking Lena’s behavior and looks. The copy doesn’t allow Lena to escape. She finally manages to trick the copy into holding onto an open grenade which goes ablaze. Lena’s copy is following the original’s desire to fight the Shimmer and starts touching everything around her to ignite it. Finally, flames fully engulf the lighthouse, the various constructs in the area collapse, and the Shimmer fades away.
Lena returns to the secret base where Kane is held. They interrogate her. She feels like she’s been there a few days, maybe weeks. They tell her it was four months. They tell her his condition improved both physically and mentally after the Shimmer vanished. Lena visits Kane and asks if he is really Kane. He replies, “I don’t think so”, and in return asks if she is Lena. She does not answer. Kane’s doppelgänger embraces Lena and their irises shimmer.