Shortly after David Abbott (Mark Ruffalo) moves into his new San Francisco digs, he has an unwelcome visitor on his hands: winsome Elizabeth Martinson (Reese Witherspoon), who asserts that the apartment is hers -- and promptly vanishes. When she starts appearing and disappearing at will, David thinks she's a ghost, while Elizabeth is convinced she's alive. Their quest for the truth ultimately leads to love in this spectral romantic comedy.