Hannah (Lili Taylor) is fatally injured in a car accident; and her spirit migrates into the body of her unconscious daughter Samantha (Olivia Thirlby) when Hannah dies on a gurney next to her. Hannah resolves to keep her daughter's life running smoothly in preparation for her potential return. Hannah, living in Samantha's body, endeavors to keep up an emotional relationship with the husband/father, Ben (David Duchovny), which sometimes veers perilously close to becoming physical, to mutual horror. Her experience helps her to learn a lot about the previously unknown (to her) life her daughter was living and helps her to see how harrowing a teen's life can be in these times, as she struggles to walk the tightrope many teens must negotiate. She's confronted by conflicting pulls between the alluring attractions adolescents face every day and the demands of schoolwork that she finds largely unfamiliar to her, since a couple of decades have passed since her own graduation. As she discovers, Samantha's life has been a challenge to meet her parents' expectations for academic excellence and behavior in an acceptable range, all the while being overwhelmed by the hormones of adolescence, in many ways more powerful than any of the drugs the kids experiment with. It is at times difficult for her to keep that grip; but, for Ben, the possessiveness he feels toward his wife's soul in his daughter's body threatens to completely overwhelm his life as well as hers, with nearly disastrous results.