Mamma Mouse lives with her three offspring in the roof of a house, where drafts in the rafters cool them in summer, and the nearby chimney warms them in winter. (Papa Mouse is no longer with them; he did not survive his encounter with a trap.) The mother mouse spends her nights foraging for food, gnawing through walls and into the flour barrel in the kitchen. She warns her brood to remain safe in their nest when she is gone.
Her three children are Hickory, Dickory, and Dock. Among them, Dock is the troublemaker; he urges his brothers to take a little walk when their mother is gone. The three little mice make their way through the house, and down the stairs; they find half a bun dropped by the little girl of the house, and feast. They are startled at first by the ticking of the tall clock in the hall; but the clock ignores them, and they gradually grow bolder.
Dock goes so far as to climb up inside the clock; he sees something shiny at the top, and wonders if it is good to eat. As he is about to bite into a glistening metal wheel, however, the works strike one o'clock in the morning. With a scream of terror, Dock runs down the clock as fast as he can go. In the hall, his brothers have already fled up the stairs; Dock follows them.
The little mice confess their adventure to Mamma Mouse when she returns in the morning. Since she thinks they have already been punished by their fright, she does not scold them; she merely reminds them of their father's fate, and warns them to obey her. The three have learned their lesson.
This is one of the minority of fables in Baum's collection in which animals talk. (See "The Black Sheep," "Pussy-cat Mew," and "Little Bun Rabbit.") Note, however, that the mice talk only to each other.