Hieronymus Merkin (Anthony Newley) has recently turned forty, and is in the midst of preparing a movie that details his life's history and development. Portraying himself as a marionette being controlled by an unseen puppet master, young Merkin is led away from the innocence of youth and into the waiting arms of one woman after another by Goodtime Eddie Filth (Milton Berle). With Filth's guidance, Merkin steadily transforms into a self-centered womanizer, save only for the longing he feels for his one lost love, Mercy Humppe (Connie Kreski). As the producers of his life story scream for him to come up with an ending, Merkin must look back and decide what, if anything, he's learned from his experiences.