Seven friends arrange a reunion at a secluded holiday home in Ireland. Unfortunately for them, a fiery sink-hole has opened up in the mountains nearby, spewing out sulphur and causing a nauseating smell outside. They might be confined to the house, but the friends are still determined to have a good time. As the weekend progresses, some of the group start behaving out of character. Before long they realise it's not just a sink-hole that has opened near their home, but something far more horrific – a portal that unleashes a sinister supernatural presence.