The Twin (1984)

Every parent's worst nightmare is just the beginning for Rachel's ordeal as in the aftermath of a tragic accident, she and her husband Anthony decide to move to the other side of the world to focus on their surviving twin son Elliot. What begins as a time of healing and isolation in the Finnish countryside turns into a desperate battle for the very soul of their son as an entity claiming to be his dead twin brother takes over Elliot — setting Rachel on a diabolical journey to unravel the horrible truth about her twin son.