A group of eight school friends take a trip to a mountain cabin as a final goodbye to one leaving for study abroad. Their reminiscing uncovers hints of a mysterious ninth person hidden in the house.

Eight school friends take a trip to a vacation house in the mountains. It's supposed to be a last sendoff to a friend who's going to study abroad. The farewell has them revisiting old memories and they discover hints there's a ninth person hidden somewhere in the house. Soon, they're contending with life-threatening incidents and realize this is no ordinary farewell; a dreadful party of disaster awaits them.