Slappy- Selective Invisibility

I opened my mouth to reply—but stopped when I saw the figure float up in front of us.
Slappy.
Slappy’s ghost was a few feet away, hovering high off the ground, above the horse’s head.
“Noooo!” My shout startled Greta. She dropped the reins. “What is it?” she cried.
“Don’t you see him?” I shouted.
She shook her head. “See what?”
Slappy tilted back his head and laughed his rattling cackle.
Lightning lurched. She raised her head.
The horse saw Slappy!
Still cackling, Slappy floated closer. The horse let out a loud, whinnying protest—and rose up onto her back legs.
I started to slide off. I uttered a cry and grasped the saddle horn.
I saw the confused look on Greta’s face. She made a frantic grab for the reins.
Missed.
The horse whinnied again. She bucked her head up and down, then took off, galloping into the trees. Off the path. Into the woods.

- The Ghost of Slappy, chapter 27