Louis won't let his little brother join a big kid's game with Bop, worried he's too little and might get hurt. Boo plays with Cubby instead, and they pretend to be the biggest kids ever.

When Pa needs mint to make ice cream, he asks Bop and Boo, playing costumed superheroes, to find more. The duo meet Buster, a proud pup determined to be a search-and-rescue dog.