Dennis Mitchell (Mason Gamble) is a five-year-old boy who lives with his parents, Henry (Robert Stanton (actor)) and Alice (Lea Thompson) in Evanston, Illinois, and is the bane of next door neighbour, George Wilson (Walter Matthau). One morning, George (or "Mr. Wilson" as Dennis calls him) pretends to be asleep in order to avoid dealing with Dennis. Dennis enters his bedroom, only to find him asleep with by his prescription medication on his night stand, and assumes he's sick. To make the man feel better, Dennis flings an aspirin into his mouth with a slingshot, causing him to gag and spit the aspirin out, as Dennis flees home.