It started about three weeks ago, when about 20 children from the Elsa Perea Flores School in Peru became violently ill.
They displayed the same terrifying symptoms; muscular convulsions - some developing into full blown seizures - fainting, vomiting, delirium and frothing at the mouth.
The children, all aged between 11 and 14, shared another unsettling trait - a shared hallucination involving being chased by a "tall man in black with a beard" who was trying to kill them.
Since then, between 80 and 100 children from the school have been affected by what education officials are calling a mass case of "contagious demonic possession or interference".
Video footage recorded at the school shows screaming children being taken by trucks to nearby hospitals. Other children are seen lying on school desks surrounded by classmates and teachers who switch between comforting and restraining them as they wait for medical help to arrive.