The story focuses on three people and the love affair that happens between them. Edmund, the son of wealthy New York businessman, his wife Zoe, and a 19-year-old girl named Karina whom Edmund brings home to satisfy his wife's request to explore a different kind of relationship. When Edmund tells his friend Jeff about it, Jeff says that Edmund has found a unicorn - a bisexual girl who wishes to have a sexual relationship with a man and a woman. Karina lays out the "rules" of the relationship that she expects Edmund and Zoe to follow. "First rule - there are no strings. I am here to please you both but not to love either of you. Rule number two - I don't play favorites. I'm not going to become your mistress or Zoe's bestie. Rule three - when I want out, I'm out, and you won't see me ever again after that. Final rule - until then I sleep exclusively with the two of you and no one else." Complications arise when both Zoe and Edmund don't follow the rules.