The Caterpiller's Question

Tappy was thirteen, blind, crippled and mute. Jack was hired to drive her across the country to a place where they were supposed to help her, but Jack wondered. They said she could speak if she wanted to badly enough, that the condition was hysterical. As they drove, he found himself liking the young girl and becoming more and more intrigued with her behavior. Why did she want to stop and walk around in the middle of nowhere. Perhaps Jack would regret his wanting to know when they both disappeared somewhere... else?