A love story revolving around five relationships in Los Angeles, all of which are put through the paces during the course of one February 14.

An army officer is on leave from Iraq on a flight to Los Angeles. On the same flight is a gay man (Bradley Cooper) whose lover is a closeted football player.

The owner (Ashton Kutcher) of a flower shop proposes to his girlfriend (Jessica Alba), only to realize he is in love with his close friend (Jennifer Garner), who discovers her boyfriend is married.

A happy retiree (Shirley Maclaine) confesses a long-ago affair to her husband.

An assistant (Anne Hathaway) working at the biggest talent agency in town is dating a mailroom assistant, while a publicist (Jessica Biel) unlucky in love has no date on Valentine's Day.