I thought it was only in two parts? I watched it feeling 'just where can this go' so am giving it the benefit of the doubt. If they have found out the identity of the child who was kidnapped, then where are the ghostly noises etc coming from? Very strange.
I think it is supposed to hark back to the satanistic past of the house but may go further back as the antiques lady said it had always been a strange place before that.