The movie is adapted from the novel "Delilah and Her 20 Exes". Ellie (Anna Faris), a single girl with a very good relationship, suddenly read in a magazine that "a woman who sleeps with more than 20 men may be single for life". This argument shocked her and she decided to go back and look for her past "bedmates". Neighbor Colin (Chris Evans) hid in Ellie's house to escape the love debt of a woman. The two of them got to know each other after a fight, so they reached an agreement that as long as Colin helped Ellie find the ideal other half from the "bedmates", she would unconditionally provide a safe haven for him to hide from women! Colin began to search and arrange Ellie's itinerary like a secretary, so that Ellie and the "returning grass" would date one by one, and he successfully ran away after one-night stands. While Ellie was still fantasizing that these ex-boyfriends might have grown taller, become more handsome or become successful, her alliance relationship with Colin began to change...