A foggy morning is a wonderland for a curious child in Trotter’s debut. Polly is disturbed when she awakens one morning to see that her familiar world has disappeared. Her wonderfully engaged Mama explains to her that fog is “damp air that you can see,” and accompanies her on an early morning walk of discovery. Each time they stop at a familiar landmark, Polly looks back at the previous one and remarks that it’s gone. Her mom reassures her it’s still there, wherein Polly asks, “How do you know?” The answer is always, “I just do.” Polly gets her own chance to respond in kind when her loving mother tucks her in bed that night. How does she know her mom loves her? She just does. With some work, this could be a springboard to a lesson about context clues: How do the characters know? Downing’s watercolor illustrations perfectly evoke a foggy morning with smudged and grayed-out backgrounds and dew settling on the vegetation. A heartwarming look at the bond between an inspiring mother and her child as they share the natural world with each other. (Picture book. 3-7)