Two couples Mr and Mrs Chan ( Mrs Chan played by Maggie Cheung ) and Mr and Mrs Chow ( Mr Chow played by Tony Leung Chiu Wai ) move into the same building on the same day. Both spend much time alone as their respective spouses work long hours. One day they discover when talking things over that their spouses are having an affaire. The two lonely hurt people come together as friends and try to reproduce the infidelity of their husband and wife whilst analysing just how it happened. Deciding in doing so to avoid the usual clich