Plot
An interviewer questions Thomas Harbor, the man who scientifically proved the existence of an afterlife, a discovery that led to an extremely high suicide rate. The interviewer asks Harbor if he feels responsible, and he says no. Directly after, a film crew member kills himself on air.
On the second anniversary of the discovery, Harbor's son Will travels on a ferry where he meets Isla. They have a conversation and he notes she looks very familiar. Will says he is upset people keep killing themselves, while Isla thinks it's an easy way out. He shares a memory he had while being dead for a minute, where he saw a young boy at a beach.
Will's brother Toby picks him up and drives him to an isolated mansion where their father is continuing his research. Will notes the large number of helpers, who Toby says used to be suicidal and now have a new purpose. He meets Lacey and Cooper, his father's aides. Thomas is periodically "put under" and revived while hooked to various machines. When they speak, Will blames him for starting a cult and for the high suicide rate. He announces his intention to get Thomas to recant his statement about the afterlife to stop the suicides.
Later, Will sees Isla on the beach preparing to commit suicide. He barely saves her and brings her to the mansion, where she is taken in. At a later meeting with the occupants, Thomas reveals his new work - a machine that can record what people see in the afterlife.
To test the machine, Toby, Will and Isla steal the corpse of Pat Phillips from the morgue. Will reveals to Isla the reason for his resentment towards his father: his mother killed herself when Thomas was too distracted with his work to notice her.
Phillips's corpse is hooked to the machine, but nothing happens. After everyone leaves, Will undoes his earlier sabotage on the machine. Immediately the screen shows a video sequence of Pat Phillips driving to a hospital, visiting someone and fighting with a woman there. Will visits the hospital, but finds the hallway from the video gone.
During a meeting, Thomas confronts Lacey about telling others the test failed and expels her from the mansion. Will shows Isla the recording, theorizing that the machine records memory rather than the afterlife. They find a record of Pat Phillips's father, who died in the hospital. Further investigations reveals the events in the recording don't match what actually happened. Pat never visited his dying father in the hospital.
Isla confides in Will that she had a son, who died while she was asleep. Isla and Will grow closer together and share a kiss, which is interrupted by Toby.
Together they rush to Thomas, who is hooked to the machine. They observe he is seeing the night their mother killed herself, except that he stops her. They are able to revive Thomas, who concludes the afterlife is an alternate version of their existing life, only with different choices made. They agree to destroy the machine, as this revelation would provoke millions of suicides by people wanting to improve the lives they have. Thomas prepares to hold a speech, which is interrupted by Lacey shooting Isla, claiming she has just "relocated" her. She dies in Will's arms.
Later, a devastated Will hooks himself up with the machine. He arrives back on the ferry, where he meets Isla again, who states this is a memory. It is revealed Will is living in a memory loop trying to prevent Isla's death, restarting on the ferry every time. Isla says he saved her and they both will move on now. Although Toby and Thomas try to revive Will, he dies, promising Isla to remember her.
In an alternate reality, Will stands on the beach, where he sees a little boy and gets him out of the water. The little boy's mother, Isla, arrives and thanks him. They don't recognise each other. After she leaves, he walks away, but starts to experience a sense of familiarity at who Isla is, even though he has never met her in this reality. A sense of knowing someone he has never met but he doesn’t know how. He stops and slowly looks back and appears to make a decision to follow his intuition and go to be with her. A post-credits scene shows Toby playing guitar in the meeting room, all the seats empty.
