A US politician (Sam Waterston) visits his poet friend (John Heard) in Mont. St. Michael, France. While walking through the medieval island discussing their philosophies of life they happen upon Sonja (Liv Ullman), a scientist in recluse, who joins in their conversation. The two men listen to the ideas of this brilliant woman and discuss how her ideas can work in their own politician and poet lives.
Big Baby tells the story of Adam Lewis, a successful horror screenwriter struggling for inspiration for his latest script. After a graphic and realistic nightmare of a hulking man dressed in a baby mask and onesie who axe murders his girlfriend Kate in the middle of the night, Adam gets the inspiration he needs for his new screenplay. Excited about the direction his story is taking, he starts losing himself in his script. Things are better than ever for Adam and Kate until “Big Baby” starts appearing in real life and tormenting and killing victims fueled by his own revenge. Characters from Adam’s script begin to pay him visits pleading for their lives, and he quickly realizes he holds their fate in his hands. Power and fear completely consume Adam until his girlfriend Kate is terrified of the man she once loved.