The final season sees laid-back contractor Frank Lambert (Patrick Duffy) and type A beautician Carol Foster (Suzanne Somers) continue their efforts to mold their mismatched, spirited broods into a single harmonious family. Brainy Dana Foster (Staci Keanan) continues her studies at the local college, while J.T. Lambert (Brandon Call) and his BFF, Rich Halke (Jason Marsden), enjoy the working world. Karen Foster (Angela Watson) is still the most fashionable student in school, while her age-mate step sibling, Al Lambert (Christine Lakin), is still the toughest tomboy around. Fifteen-year-old prodigy Mark Foster (Christopher Castile) sees his research branching out from genetics... to include girls! And 6-year-old Lilly tries to make sense of both of her family branches. The conflicts are endless as Frank and Carol try to keep their household of children, ages 6 through 20, in check, but the Fosters and the Lamberts take each day Step by Step.