Lena (Natalie Portman) is undergoing a quarantined debriefing about an expedition she participated in — into an anomaly called “the Shimmer.” Earlier her husband Kane, an Army Special Forces soldier had went into “the Shimmer” and was the only one to return. But when he returned he remembered nothing and became suddenly ill. Lena is a cellular biology professor, who was sent into the Shimmer with four other female doctors to try and get answers where the soldiers couldn’t. Their goal is to reach a lighthouse where the Shimmer first appeared. Nearly as soon as their mission begins guidance technology fails. The team also begins to forget extensive periods of time. They wind up at an abandoned military base where Lena learns was one of her husband’s last stops. They discover video on a memory card which shows Kane cutting open a living expedition member which reveals a snake-like creature moving inside him. That night the perimeter fence is ripped apart. Members begin to fight among themselves, some wanting to turn back and others wanting to push forward.