Pugsley (Ken Weatherwax) and Wednesday (Lisa Loring) start a row at a birthday party when their gift of a tarantula upsets Harold (guest star Kim Tyler), the birthday boy. Harold's parents insist that the Addams children lack breeding and, therefore, are no longer allowed to play with their son. Gomez (John Astin) and Morticia (Carolyn Jones) then hire a genealogist to trace their heritage.