Coming home to Milwaukee after a summer playing with the band in Chicago, Joanie Cunningham tries to convince her over-protective father that she's mature enough to move away from home and continue her career in the Windy City.

Howard's teen-aged niece, K.C., comes to stay with the Cunninghams after a scandal closes her Houston boarding school while Fonzie hopes a night at the circus will help him win little Heather's heart when nothing else seems to work.