 For the episode "Union Station", in order to keep Sherry  Stringfields departure a secret, false copies of the script  circulated amongst the production staff. Only writer Carol Flint,  director Tom Moore, the shooting crew, Stringfield, and Anthony  Edwards knew the ending ahead of time, and it was filmed on location  in Chicago the Saturday before the episode was slated to air. Editor  Kevin Casey got a call the following Monday from a confused  assistant saying that the footage of the final scene which had just  arrived did not match the script. Flint eventually set them both  straight and Casey went to work, editing right up to the airdate.  NBC didnt even know what was actually going to happen before the  episode aired.