Likeable 6th grader Liam writes to Santa asking him to prove that he's real. But Liam is dyslexic and accidentally sends his letter to Satan instead, who shows up at Liam's house, excited to have his first fanboy letter and wanting a little of Liam's soul.
13 years after being impregnated by Satan, a reluctant mother, Laura, and her Antichrist daughter, Chrissy, attempt to live an ordinary life in Delaware, but are constantly thwarted by monstrous forces, including Satan, who yearns for custody of his daughter's soul.