After his family rushes out the door for the first day of school, Peanut Butter the dog finds himself all alone for the first time. Bored, curious, and lonely, Peanut Butter sneaks out of the house in search of an adventure. He encounters new animals, explores new places, smells new smells, and even makes a friend. But before he realizes it, the day is nearly over, and he must race home before the kids get off the bus and find out he hasn't exactly been a good dog.