After a Celtic metal object is removed from a dirt mound behind their inherited mountain home outside Cahir, Ireland, the Murphy family experiences several unexplained events including the disappearance of their eldest son Tevan. With no other place to turn, Patrick and Ansley Murphy enlist the help of Liam McNamara and his Irish Paranormal Pinkertons team who find that the dirt mound is actually a stone structure. They call in Dr. Sean Ryan, a medieval archaeologist, who discovers that the structure is the northeast tower of a castle that has been buried for centuries. After intensive research, the team uncovers its strange history and even stranger occupants. In order to retrieve the boy in the netherworld, another dimension, they must map the castle. In doing so, they discover something terrifying down in its recesses. With the knowledge of the castle layout, the team bravely enters the netherworld to retrieve the captive boy and finds a bigger danger waiting to be unleashed on the world. Will the rescue go as planned? Can they stop the evil waiting to be unleashed?