Greta's last name, "Hideg", is the Hungarian word for "cold".
The film is set in New York, but was actually filmed in Ireland. However, the subway station scenes where the trains enter the station were filmed in Toronto.
The original title of the film was "The Widow".
The distribution rights for the film were bought at the Toronto International Film Festival by Focus Features for $6 million.
The restaurant scenes were shot over the space of a week. By the end of the week, the smell of fish on set was so bad, it made people need to leave early.