The world is plagued by a mysterious force that manipulates people’s negative emotions, leading them to commit suicide. The film starts in a dimly lit skating rink in Barcelona where Sebastian watches his daughter Anna skate. Sebastian and Anna are attacked by a group of blind intruders seeking their supplies. After the attackers leave, Sebastian and Anna, wearing blacked out goggles, venture outside into the sunlight.

They encounter a group of survivors, and Sebastian expresses his desire to join them. He reveals his background as a former construction engineer and states he knows where they can find generators that can provide light and heating. Sebastian instructs Anna to only come to him when called. Inside a bus terminus/warehouse, he meets the rest of the group and is told in the past some members were attacked by “seers” – individuals seemingly unaffected by the malevolent entity who try to get others to see the entity.

The next morning, with everyone asleep inside a bus, Sebastian locks the driver’s compartment, starts the engine and drives the bus outside. Everyone is left without blindfolds and several are injured. Sebastian is revealed as a seer who believes the entity is a divine being saving humanity through death. His daughter is actually an apparition who pushes him to get others to face the creature. Following Anna’s instructions, Sebastian leads each member to open their eyes one by one. Upon witnessing the entity, each person takes their own life.

In a flashback from 9 months earlier, Barcelona falls under the grip of the unseen entity, causing its residents to try to flee in terror. Sebastian retrieves Anna from school but tragically loses his wife in a car accident. Seeking solace and safety, he finds refuge in a church and meets Esteban, a Pastor who believes the entity is an angel. Esteban proposes that humanity should be liberated from suffering by embracing death. Sebastian and Anna try to hide but one day a group of seers led by the Pastor discovers their hiding place and captures the two. The pastor forces Anna to open her eyes, leading to her untimely demise. Sebastian then sees the entity but instead of taking his life, his daughter reappears to him.

Sebastian encounters another group of survivors led by Rafa, accompanied by his loyal dogs. The group includes Octavio, a delivery guy with a background in physics; Roberto and Isabel, a couple; Claire, an English psychiatrist; and Sofia, a young German girl separated from her mother. Sofia shares information about a mountain castle, Montjuic, believed to be a safe refuge from the entity. Determined to reach the castle, the group embarks to Montjuic. Rafa loses his life early in the journey after Sebastian sabotage the dog leashes, and the remaining survivors take shelter. Octavio theorizes that the entity is a quantum being that perceives human emotions, particularly fear and grief. Sebastian leads Octavio to his death but starts to doubt Anna and the rightness of his actions. The remainders continue the journey but Roberto and Isabel lose their lives. Claire suspects Sebastian’s true nature as a seer and shields Sofia from him. Sebastian who has started to resist Anna’s influence, convinces Claire and Sofia that he means no harm and vows to protect them.

The pastor and his followers find Claire, Sofia and Sebastian. Sebastian helps Claire and Sofia get to a lift then confronts Esteban. The men fight and both succumb to their wounds, but Sebastian finds solace knowing he guided Claire and Sofia to safety.

Claire and Sofia reach the mountain castle which is revealed as an army camp. Sofia reunites with her mother. Claire undergoes tests in a laboratory to develop an antibody that can provide immunity against the entity’s influence. In the concluding scene, the researchers administer the antibody to rats in a secure containment room. One of the experimental subjects, a seer watches anxiously as an ominous growl emanates from the room. The seer urgently requests to witness what unfolds.