A school field trip to an ancient castle goes terribly wrong for a group of friends, when a dangerous storm erupts. As they are about to leave the castle, four friends are cornered by the class bully, who tries to pull one of his usual pranks. Instead, they all fall down a tunnel that transports them a future where mankind is nearly extinct nature has taken control. The friends will have to face up to this hostile new world if they are to work together and have any chance of making it back home.