On the outskirts of Dublin City, a young couple's relationship hangs by a thread. Isolated and stressed, disputes turn physical, leaving a pregnant Erin Greene in a poor state of mental health, and Philip Montague wanting an escape. They decide to go on a drive and head for Erin's favourite place as a child, the Wicklow Mountains. However, a simple oversight leaves them both stranded, with no fuel and a blizzard due. With no other choice, Philip heads off to the nearest town in search of help, leaving his fiancée alone. With Philip gone and the inevitability of a snowstorm looming, Erin, in order to survive, must battle against her plagued mind and the supernatural elements that lie hidden deep in the hills.