What is Tom's dream?

The morning after Tom returns from the island, Aunt Polly rebukes him for having made her suffer so much and for not having given her some hint that he was not actually dead. Tom argues that doing so would have spoiled the whole adventure, but he admits that he “dreamed” about everyone back in town. Telling her his dream, Tom relates everything he saw and overheard when he crossed the river and sneaked into the house a few nights earlier. Aunt Polly seems amazed by the power of Tom’s vision and forgives him for not having visited her. Sid, meanwhile, wonders suspiciously how this dream could be so precise and detailed.