In suburban Nebraska, a group of partying high school teens jokingly dare their friend Charlie to look into the mirror and repeat "Bloody Mary, Bloody Mary, Bloody Mary," not knowing this will unleash a series of mysterious murders. Sam and Dean realize that Bloody Mary has the power to travel through all reflective surfaces when she is hunting a victim. Worried that teens are accidentally summoning Bloody Mary, Sam and Dean race to destroy the violent spirit before she can kill again.