From moviepooper.com
Audrey Fleming(Lindsay Lohan) has a twin sister named Dakota Moss(Lindsay Lohan) that was separated at birth. Susan Flemings real baby died at birth and a junkie woman down the hall had twins, so behind Mrs. Flemings back Daniel Fleming pays the junkie to keep one of the twins. The real Aubrey was kidnapped by a serial killer (who turns out to be her piano instructor Douglas) and while he's torturing her, in another town Dakota is having the same exact things happen to her unexplainably (turns out to be they're stigmatic twins). So Dakota comes to her town to find out what is going on and is found severely injured on the side of the road so they believe its Aubrey. Dakota spends the whole movie trying to prove that she isn't Aubrey. She eventually finds out what is going on and Mr. Fleming helps her get to the killer. Douglas kills Mr. Fleming then Dakota kills Douglas and in the nick of time finds Aubrey who was buried underground and digs her out from a shallow grave.
In atonement, Robbie is convicted, goes to prison, gets out, goes to the army, meets the girl again, she says she loves him and he says to wait for her. Turns out he's innocent and it was a houseguest that was the rapist. Robbie dies in the war before they can be together. The girls dies in a weird flood.