Two high-school sisters, Stacey and Emma, have recently moved to a suburban area in California. Emma struggles to integrate into the community while Stacey quickly makes new friends and has a local boyfriend, CJ.
Emma befriends Evan, her neighbor. Stacey and Emma’s parents have a strained relationship, and her mother is out of town. Emma’s best friend begins displaying unusual behavior at school, eating constantly and coughing up blood. She collapses in the school parking lot and Emma and another boy find her in a seizure-like state. The boy urges Emma to get help, but before she can return, Gracie vomits blood all over the boy.