A charming and very daring thief known as Arsene Lupin is terrorizing the wealthy of Paris, he even goes so far as to threaten the Mona Lisa. But the police, led by the great Guerchard, think they know Arsene Lupin's identity, and they have a secret weapon to catch him.
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.