Telly Paretta (played by Julianne Moore) is haunted by the memory of her 8-year-old son, Sam, who died in a plane crash over a year ago. She attends therapy sessions and takes medication to help deal with her grief. However, one day she wakes up to find all evidence of her son's existence has disappeared. His bedroom has been turned into a storage room, and her husband, Jim (played by Anthony Edwards), claims they never had a son.
Telly becomes convinced that she is not crazy and that her son did indeed exist. She meets a father named Ash (played by Dominic West), who has had a similar experience - his daughter was also on the same plane as Telly's son. Together, they try to piece together what happened to their missing children, but soon find themselves pursued by mysterious forces who will stop at nothing to keep them from the truth.
As Telly and Ash unravel the mystery, they discover a secret government project involving brainwashing and mind control. They realize that their memories have been manipulated and their loved ones erased as part of a larger experiment. In the end, Telly and Ash are able to break free from the project and reunite with their missing children. The film ends with Telly triumphantly walking down the street with her son, Sam, in her arms.