Eleanor (Jillian Bell), a young and inexperienced fairy godmother, hears that the profession of fairy godmother is in danger of disappearing. She wants to take action to prove that people still need fairy godmothers, so she asks a letter from an unhappy ten-year-old girl to help her. But when she finds the "little girl" Mackenzie (Isla Fisher), she finds that she is now a 40-year-old single mother, and the experience of life makes her no longer believe in "happy life". Eleanor decided to help Mackenzie find happiness, whether she liked it or not.