Set in 1920's New York City, this movie tells the story of idealistic young playwright David Shayne. Producer Julian Marx finally finds funding for the project from gangster Nick Valenti. The catch is that Nick's girl friend Olive Neal gets the part of a psychiatrist, and Olive is a bimbo who could never pass for a psychiatrist as well as being a dreadful actress. Agreeing to this first compromise is the first step to Broadway's complete seduction of David, who neglects longtime girl friend...

An apparent murder-suicide in a hospital emergency room leads to an investigation by the on-call doctor, which reveals a plot by an insane toymaker to kill as many people as possible during Halloween through an ancient Celtic ritual involving a stolen boulder from Stonehenge and Halloween masks.