After giving his class a lesson on dilution, John theorizes that by diluting the Fountain of Youth water with regular water he will be cured of his strange morphing phenomenon. Neighbor Mrs. Kimberly (Sandra Gould, "Bewitched") drops in to the Martin household hoping John will babysit her infant grandson while she runs errands. When John leaves the room, Marjorie and Ricky return home to find the crying infant. They feel the dilution experiment backfired and he reverted to being an infant. They take the baby into the sun to try and evaporate the water. John returns to see the baby missing and assumes Mrs. Kimberly returned to take her grandchild, but goes in search of her to make sure. Meanwhile, Marjorie and Ricky look through John's journal in hopes of finding a cure. When John can't find Mrs. Kimberly he files a missing persons report with Sergeant Cook (Jonathan R. Banks, "Breaking Bad", "Better Call Saul"). Marjorie takes the baby to a psychiatrist, Dr. Jerome Hansen (Ivor Francis), to explain the situation. Comical complications ensue.
Some nice comedy in this episode.
