Chris Kelvin (GEORGE CLOONEY) is a psychologist who's focused on his work after the untimely death of his wife, Rheya (NATASCHA McELHONE), several years ago. Both of those factors are the reason his close friend, Gibarian (URLICH TUKUR), has sent him an urgent communiqué requesting him to come and investigate the strange occurrences and behavior being experienced onboard his space station, the Prometheus.
Orbiting the planet Solaris, the station's crew has been investigating its economic potential as a viable commercial property or possible energy source. Yet, it seems that the planet has similarly been examining the crew and has created a situation that they don't want to leave, but which is driving them mad.
When Chris eventually arrives on the Prometheus, only two of its crewmembers, Gordon (VIOLA DAVIS) and Snow (JEREMEY DAVIES) are alive, and both are acting quite odd. Hoping to get to the bottom of what's occurred, Chris questions both of them, but doesn't get any concrete answers.
What he does get, however, changes his life and view of it. In the middle of the night, Rheya suddenly arrives, unaware that she's supposed to be dead. Chris is understandably spooked and confused about her presence, but eventually realizes that the planet has somehow read his mind and created a perfect copy of her.
Although he's initially a bit reluctant to interact with Rheya, he eventually does and soon becomes intoxicated by her presence, especially due to the tumultuous way their relationship and her life ended a few years back. Yet, as Rheya eventually begins to realize that and Gordon insists that the wife be destroyed before they head back to Earth because she's not the real thing, Chris must decide what to do about the situation.