The actress will play a groupie a rock band sacrifices as part of a deal with the devil in Jennifer's Body - but they pick the wrong girl and she comes back literally looking for blood.
Fox tells WENN, "It's a really dark comedy with a lot of secret messages lying underneath the script.
"I play the captain of the flag team and I get improperly sacrificed by this rock band, who are trying to obtain a record deal - so they sell their soul to Satan. They need to sacrifice a virgin.
"I'm not a virgin, so what happens is I get taken over by a demon and, in order to stay alive in this sort of undead period, I have to eat flesh, so I eat boys."
To prepare for the gory role, Fox conjured up her own storyline about her character being molested by her father: "It's not in the script but, in my head, my character was victimised by my dad, so I take it out on the boys in my high school.
"So it's me eating them and having this bizarre pseudo-lesbian relationship with my best friend. It's all very manipulative and is basically how frightening young girls can be - they're completely terrifying."