At their new home in upstate New York, newly widowed psychologist David Callaway tries desperately to help his traumatized daughter Emily deal with her mother's death. But before long, both David and Emily are being terrorized by someone - or something - named Charlie: a "friend" who may or may not be imaginary.
For young Emily Callaway (Dakota Fanning), her games of Hide and Seek with an imaginary friend named Charles have become anything but simple and innocent. Instead she finds herself in the middle of a series of increasingly nightmarish acts that even her father David (Robert DeNiro) cannot stop. Who - or what - is Charlie? David wonders. How can an "imaginary" entity have this kind of hold on her? Maybe Charlie is not imaginary at all, but instead a flesh-and-blood malevolent presence?