Scientists invent a brain–computer interface that records sensations from a person's brain on tape for others to experience. The team includes estranged husband and wife Michael and Karen, as well as Michael's colleague Lillian. Under CEO Alex's direction, they demonstrate the device to investors to secure financing.
Karen dons the recorder while Michael and Lillian operate the system. When Michael plays the tape back, the group realizes that not only sensations but also emotions are captured. Michael records memories of times with Karen, sharing them with her, and this leads to their reconciliation.
Alex and his investors push to recruit Landan, who works for the federal government and has military ties, onto the team. Karen strongly opposes the plan to develop the invention for military use.
One team member, Gordy, has sex while wearing the recorder and shares the tape with colleagues, including Hal. Hal then splices a segment to form a continuous orgasm, causing sensory overload and forcing Hal into retirement. Tensions mount as the potential for abuse—beyond just the military-industrial complex—becomes clear.
Lillian, a chain smoker, suffers heart problems and has a heart attack while working alone. Realizing she is dying, Lillian records the experience.
Michael decides to play Lillian's recording, but nearly dies when his body relives her heart attack. He modifies his console to filter the physical output and replays the tape, uncovering memory bubbles—moments from Lillian's life. He witnesses Lillian's memories, including a playful exchange with Michael as he manipulates an industrial robot, a surprise birthday party, and the heartbreak when Alex cancels an earlier project.
Landan's men monitor the equipment while Michael plays Lillian's tape. They have Gordy plug in, but Landan ignores warnings that Michael modified his terminal. Gordy dies from experiencing Lillian's heart attack.
Michael's playback is cut short by Hal, but witnessing the near-death experience increases his resolve to see the entire tape. Alex has the recording locked away and informs Michael he will not be allowed to view it. When Michael returns to work, he finds Landan and outside technicians going through his research records; Alex fires Michael and Karen.
Michael attempts to hack the lab's computers. Hal urges him to search for "Project Brainstorm," a military program designed to weaponize the invention. Michael accesses a tape in his den and abruptly stops, unsettled by its disturbing content. Even their son Chris views the tape, triggering a psychotic break that requires hospitalization. Alex visits, and Michael confronts him about Project Brainstorm, blaming him for Chris's condition. Alex denies knowledge of the project and informs Michael of Gordy's death.
Michael vows to destroy his work and enlists Karen and Hal. They head to Pinehurst Resort, only to realize they are under surveillance. Karen feigns a reconciliation with Michael while secretly leaving for Hal's house. Michael then accesses the Brainstorm system through another phone line, and Karen sabotages the robots that manufacture the interface terminals. The facility descends into chaos.
Karen disables the security system, locking the staff out. Michael loads Lillian's tape. With the plant in turmoil, Robert orders Michael's arrest.
Karen reunites with Michael at a location meaningful to them. Hal and his wife Wendy send the last commands to shut down the company computers. Karen shadows Michael to a phone booth at the Wright Brothers memorial; the tape plays. Michael experiences an afterlife—seeing hell, traversing the cosmos, and encountering angels and departed souls moving toward a cosmic Light. He collapses. Believing him dead, Karen screams and begs him to stay. When he awakens, he whispers, Look at the stars.
> Look at the stars!
Their embrace, preserved inside a memory bubble, drifts into the night.
