Ben, Hannah and Samantha "Sam" Marris are a normal middle class American family. Sam's in a rebellious stage at 16 though, finding her mother very uncool and embarrassing, dismaying Hannah. One day when the two are arguing in the car, they get into an accident. Both of them end up in the hospital, where Hannah dies of her injuries. Sam wakes up... only it's not her anymore. Hannah has someone entered her body, to her shock and confusion on waking, along with Ben's initial disbelief. When he accepts that it's her, they must now deal with this incredible occurrence.
The film stars David Duchovny (Ben), Lili Taylor (Hannah), and Olivia Thirlby (Sam). It was produced in France, and Vincent Perez directed. Not to be confused with a 2006 "documentary" that's based on the book, nor a number of other films with the same or similar names either.
It's French title is Si j'étais toi (If I Were You) and is a remake of Himitsu, a Japanese film released in 1999.
- Attempted Rape: Hannah clearly thinks Ethan, Sam's boyfriend, is doing this when she's suddenly grabbed by him. It turns out they like role-playing (though Hannah isn't happy to learn Sam is having sex) and this was consensual between them. The fact that Hannah's not in on the game however nearly makes it rape for real with her though.
- Brainy Brunette: Sam is a brunette honor student who's intent on getting into an Ivy League school. She doesn't fit most stereotypes though, being a rebellious girl who's sexually active, uses drugs and doesn't dress or act nerdy at all.
- Bratty Teenage Daughter: Sam is a moody, rebellious 16 year old girl who thinks her mom's too uncool to bear and dislikes being around her most of the time. After her mom's death, though, it's made clear she really did love her even so-she's just at that age.
- Cassandra Truth: No one believes Hannah is trapped in Sam's body at first. Over time Ben realizes it's true, but they don't try to convince else, as obviously they realize it would just cause problems, and act like Hannah is Sam.
- Floating Head Syndrome: The poster has David Duchovny and Olivia Thirlby's faces like this (see above).
- Missing Mom: Hannah dies of her injuries from a car accident early on, but then lingers while in her daughter Sam's body. However, when Sam's soul becomes dominant briefly, she's desperate to find out where Hannah is, not remembering what happened. After she's returned fully and Hannah is gone, Sam remembers, accepting her mom's death. They were already estranged, though Hannah tells her in a video tape she leaves behind she's come to understand her better. Because of this, the pair have a posthumous reconciliation.
- Only Known by Their Nickname: Sam is rarely called by her full name, Samantha.
- Out-of-Character Alert: A lot of people she knows notice Sam is acting oddly, though most of them just think it's as a result of her mom's death. None of course suspect that "Sam" is really her mom Hannah in Sam's body.
- Parental Incest: Being in her daughter's body means things get very awkward between Hannah and Ben. He chides her for acting overly affectionate while they're at a restaurant, and later she's quite suggestive toward him while wearing a pretty revealing nightie. They never actually cross the line, but it was obviously difficult for them still wanting intimacy but unable to because of the bizarre happenstance.
- Riddle for the Ages: There is never even a hint as to why Hannah and Sam were Sharing a Body. It appears to be just something that can happen sometimes in the film's universe, since Ben finds another case where this happened in Africa too, triggered by a sudden death (though those involved had no connection, unlike Hannah and Sam).
- Romancing the Widow: Hannah is jealous of Ben's patient (Sam's guidance counselor) flirting with him while having their appointment (he works as an opthamologist), though Ben insists he wouldn't act on it. The woman is also unaware that Hannah's (kind of) still around, in Sam's body.
- Sharing a Body: In an unusual twist, when Hannah's body dies her soul somehow gets into her daughter Sam. At first it's left unclear where Sam's soul has gone, but it turns out to be dormant still. Sam comes out after Hannah used Ketamine, before reverting. They finally switch one last time, and Hannah leaves for good.
- Something Only They Would Say: Ben is convinced that Hannah is really in Sam's body due to her relating anecdotes from their past and speaking the way that she did. At first he just thinks Sam must have heard it from Hannah, but soon accepts that it's really her.
- Title Drop: Near the end, when Sam "wakes up" Ben says he has to tell her a secret (about her mother sharing her body), which they kept from everyone else since it would seem too absurd.