Trevor Davis, a family doctor in Phoenix, Arizona, is happily dating Melanie, a pharmaceutical representative for a weight-loss medication. His world is turned upside down when Shannon, an attractive pharmaceutical representative for a competing weight-loss medication, begins visiting his clinic. Trevor falls head over heels for Shannon and starts prescribing her weight-loss medication exclusively, completely forgetting Melanie. Trevor couldn't be happier until he discovers that a friend of his is dating a pharmaceutical representative named Shannon and the two Shannons have the same birthdate. Enlisting a reluctant Melanie's help, Trevor tries to find out who Shannon really is. However, Melanie abruptly breaks off her relationship with Trevor via voice mail and moves away from Phoenix overnight. Trevor suspects that Melanie has instead been kidnapped by the same organization that sent Shannon to the Phoenix area. What Trevor finds as he searches for Melanie could very well result in his and Melanie's deaths.