Five-year-old Bobby accompanies Grandma to the supermarket to buy prunes because her "medicine isn't working." He doesn't want to submit to this torture, but at the store they enjoy several adventures, including a fight over a prized prune package, Grandma making a citizen's arrest of a shoplifting grandfather, and what may be Grandma's last chance for romance. Bobby gains new respect for Grandma while enduring these adventures.