Who is the antagonist in Running from Safety: An Adventure of the Spirit by Richard Bach?

I don't think there is an antagonoist in terms of character. The protagonist has his younger self as an antagonist-figure. When the angel disappears, the 59-year-old Richard finds himself facing a very angry, nine-year-old version of himself, Dickie, who has been locked away in time and space for 50 years. Young Dickie wants to learn about life, but not necessarily from the man who locked him away. Richard must find a way to reach the child and establish a connection. Doing so, he can learn about himself and find answers hidden in his past.