 Lucy is a lonely Chicago subway employee who s 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 fiance 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.