New York, 1980: three complete strangers accidentally discover that they\'re identical triplets, separated at birth. The 19-year-olds\' joyous reunion catapults them to international fame, but also unlocks an extraordinary and disturbing secret that goes beyond their own lives - and could transform our understanding of human nature forever.
Roberta is a bored suburban housewife who is fascinated with a woman, Susan, she only knows about by reading messages to and from her in the personals section of the newspaper. This fascination reaches a peak when an ad with the headline \"Desperately Seeking Susan\" proposes a rendezvous. Roberta goes too, and in a series of events involving amnesia and mistaken identity, steps into Susan\'s life.