The movie opens with an archaeological team uncovering an ancient tomb in Mexico which they quickly abandon after encountering a strange symbol carved into the walls. The scene then shifts to a British couple, Jennifer and Mark, who arrive in Mexico where Mark is attempting to reopen the abandoned mine he inherited from his father.
Upon their arrival, they discover that the local workers refuse to enter the mine due to a curse that has plagued the area for centuries. Determined to prove the locals wrong, Jennifer and Mark enter the mine and inadvertently release a demon which possesses Mark's left hand and forces him to act out in violent and destructive ways.
As the demon begins to spread its influence throughout the local community, Jennifer becomes determined to find a way to rid her husband of the demon's grip and stop its reign of terror. But as the body count continues to rise, Jennifer soon discovers that the only way to stop the demon is to cut off the possessed person's left hand.
As the situation becomes increasingly desperate, Jennifer and a small group of survivors must use their wits and courage to stop the demon before it can claim any more victims. However, even as the demon's power begins to wane, Jennifer realizes that the true source of the curse may be far more ancient and powerful than anyone had previously suspected.