Lucy is a lonely Chicago subway employee whose life consists of living with her cat, avoiding her landlord's boorish son, and nursing a hopeless crush on a handsome commuter who passes her booth every day. Whilst working the Christmas shift, she witnesses him being mugged and pushed off the platform, and manages to save his life - and is mistaken for his fiancé at the hospital. She is duly embraced by the man's warm and welcoming family - except for his suspicious brother Jack, who is not convinced that she's the genuine article.
