Katy Thatcher is eight years old, and her world is changing all around her. Katy observes what goes on around her and puts the puzzle pieces together to try to make sense of the world. Babies are being born, and there is a fire at the factory and a fire at the mill. Katy is learning how to be a doctor by watching her father at work. On one of their house visits, Katy makes a friend of Jacob Stoltz, a boy who is touched. Katy watches Paul, a neighbor, sneer at Nell after he's been kissing her in the barn. Katy watches as Nell must leave the farm. Then one night a baby appears mysteriously at Katy's house and puzzle pieces fall into place for her so she can explain the mystery and protect the innocent.