Ally Darling (Anna Faris) is a recently fired marketing executive who’s becoming concerned that she might never find "Mr. Right." Her sister Daisy (Ari Graynor) is getting married to the love of her life and her mother Ava (Meet the Parents' Blythe Danner) seems insistent that Ally move forward with her life as well.
During a ride home on the subway, she reads an article that concludes if a woman has slept with more than twenty men there is very little chance that she will get married. She worries about her seemingly large number of 19 and makes a promise to herself that the next man she gets with will be her true love. After a night out with the girls she is devastated to wake up next to her ex-boss and jerk Roger (Joel McHale). She decides there and then to look back on all the men ...