Paul (GREG KINNEAR) and Jessie Duncan (REBECCA ROMIJN-STAMOS) seem to have the perfect life. He's a biology teacher who may be moving on to a better school system, while she's a photographer. But the pride and joy of their lives is their 8-year-old son, Adam (CAMERON BRIGHT).
Yet, when he's killed in a freak car accident, their lives are shattered, as they know they'll never see him again. Genetic scientist Richard Wells (ROBERT DE NIRO) of the Godsend Institute, however, has heard of their plight and offers them a unique solution to deal with their grief.
By harvesting the DNA from their dead son, Wells claims that he can clone their son, creating a perfect duplicate of him. Paul is adamantly against it, knowing full well that such a creation might be genetically identical to Adam, but simply wouldn't be him.
Nevertheless, his and Jessie's growing grief eventually gets the best of them and they agree to Richard's proposal, moving hundreds of miles away and severing all ties with anyone who knew Adam.
Eight years later, they're right back where they were before the tragedy. Yet, when Adam passes the age at which the original version of him died, he begins experiencing odd and frightening hallucination-like occurrences.
Richard, who's now quite close to the Duncans, reassures them that it's just a common childhood condition known as night terrors. As they continue to grow and worsen, however, Paul and Jessie begin to worry that something more complicated and possibly sinister might be causing them. As they dig deeper for an explanation, they race against time to find the answer before something tragic occurs again.