Murray Bear is supposed to go to the waterfall with his sister, Molly, to meet a friend, but Murray is worried. "What if it's too LOUD?" he cries "Or what if I get swept away!" So Molly tells him about her special worry box. "When I'm worried about something," she says, "I write it down, then put it inside." She offers to help make one for Murray, and he takes it on their journey-but will it really help?