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Lifelong friends Emma (Natalie Portman) and Adam (Ashton Kutcher) take their relationship to the next level by having sex. Afraid of ruining their friendship, the new lovers make a pact to keep things purely physical, with no fighting, no jealousy and no expectations. Emma and Adam pledge to do whatever they want, wherever they want, as long as they do not fall in love. The question then becomes: Who will fall first? Wikipedia