In the process of rebuilding her life after a difficult past, Sarah and her young son, Chris, move to a new Irish rural home, alongside a forest that hides a huge cavity in the ground. A terrified encounter with a mysterious neighbor destroys the already fragile sense of security, casting Sarah into a nightmare, full of paranoia and mistrust. One night, Chris disappears, but when he reappears he seems unharmed and unchanged. However, his behavior becomes more and more disturbing, causing Sarah to wonder if the boy who has returned is really her son. The woman tries to discover if her son’s disturbing changes are related to the threatening cavity deeply hidden in the forest near her home.