The Twin is a psychological thriller that explores themes of loss, grief, and the lengths that parents will go to protect their children. As Rachel and Anthony try to come to terms with the death of their son, Elliot becomes increasingly withdrawn and uncommunicative. They start to suspect that something is wrong, and their fears are confirmed when Elliot starts exhibiting strange and disturbing behavior.
At first, Rachel and Anthony try to explain Elliot's behavior as a normal reaction to the trauma he has endured. But as Elliot becomes more and more violent and aggressive, they realize that something else is at work. They begin to suspect that the entity claiming to be their dead son is actually a malevolent force that is seeking to destroy their family.
As Rachel delves deeper into the mystery, she learns about the ancient Finnish folklore of the "kellokas," a malevolent spirit that inhabits the bodies of children who have suffered trauma. With the help of a local farmer and his wife, Rachel tries to perform a ritual to exorcise the entity from Elliot's body, but the ceremony goes horribly wrong.
As the tension builds, Rachel must confront her deepest fears and darkest secrets in order to save her family from the evil force that has taken over her son. The Twin is a heart-pounding thriller that explores the limits of parental love and the harrowing consequences of grief and loss.