After their disastrous wedding, Gary (Adam Scott) has just moved in with Samantha (Evangeline Lilly) and her six-year-old son Lucas. He tries to connect with the boy but he doesn't talk and does some peculiar things, like drawing Pentagrams on his bedroom ceiling. As the movie progresses we find out that Samantha once belonged to a cult and that her son may actually be the Anti-Christ. Gary almost leaves when Lukas knocks him out and buries him in a crate in the backyard.
This comedy follows all the usual notes of an "evil child" movie and it is actually quite funny. The kid who portrays Lucas is great in doing a Damien (from The Omen) impression. I particularly liked his evil goat sock puppet. If you're looking for some light horror then you'll like this.