What early 1980s, possibly late 1970s movie was about a little boy who is haunted by a little girl crying and singing Frère Jacques? He finds her doll in the well and when he places it on her grave, it raises up and drops and inside he finds a diamond.

Child of Glass.

This movie begins showing The Ainsworth family traveling to their new plantaion house. WHen they arive the Kids are pretty shocked at how run down the house is. Well they work on it. And you meet the Drunk Caretaker who has Murder On His Mind. One night Alexander sees a Blue Light from the hay loft of the barn. He goes out there and sees the ghost of Inez. She tells him what help she needs from him. Well Alexanders decides to help him. I don't remember the exact riddle. But it was about the 2 should touch. Well it goes on. And Alexander falls into the well. And he is found. His parents send his little friend Blossom down. And she finds the China Doll. They rescue Alexander and they go into the Cemetery into the Chapel of Inezs Family and place the doll on top of her tomb. Well the gost of Inez apperas and grabs the doll than dies and evaporates into the Tomb. THan the doll appears and falls onto the floor. The head shatters and in side the head is the long lost treasure. WHich consists of millions of dollars worth of diamonds.

https://en.wikipedia.org/wiki/Child_of_Glass