The Girl that Never Grew Up

As a child we are more susceptible to the spirit world, as we have not yet grown up and but all our childish beliefs behind us. But what if a child met a ghost when he was young and didn't forget about her when he got older? What if the ghost was a young child who always wanted things to go her way? What if, under the influence of that ghost, the boy killed a dog and was sent to an insane asylum for it because he claimed his imaginary friend told him to do it?