Sisters (2006)

A young doctor goes home with a dazzlingly beautiful young woman he meets while volunteering at a party for children at a Vancouver mental health clinic. The next day is her birthday (as well as that of her twin sister, her unseen flatmate). After a night of lovemaking, the young doctor goes out in search of a cake. Meanwhile, a reporter who crashed the kids' party breaks into the office of the physician in charge of the clinic, only to witness a murder on a closed circuit television in the doctor's office. With the help of an investigator, the reporter pursues the truth, which eventually takes her back to the clinic. Does her own past hold the key to what she'll uncover?