Samantha feels a tremendous heaviness and fatigue and when Darrin tries to lift her she seems to weigh a ton. She immediately calls Dr. Bombay.
Dr. Bombay brings a scale and it shows that Sam weighs 400 pounds. He tells her she has a condition peculiar to witches and warlocks called Gravititis Inflamitis ... an inflammation of the gravitational tendons. He gives her an antidote - but it makes her too light and she floats to the ceiling.
Mrs. Prescott, the wife of one of Darrin's clients, arrives to pick up Sam for the charity bazaar and fashion show that Sam had volunteered to help at. Darrin, who is holding Sam by the waist, must go with her. She is at her booth with a large bolt of material to keep her from floating.
Along comes Mrs. Brock who, of course, wants to buy the bolt that is on Samantha's lap. When Darrin returns Samantha has floated up to a tree. He climbs up and joins her just as Mr. Prescott shows up and threatens to take away the account.
Samantha must appear in the fashion show and she gets an idea of how to make it a campaign for Prescott shoes, Darrin's account. Carrying a huge brass urn on her shoulder, which keeps her on the ground, she half walks and half floats. She says the slogan is "With Prescott shoes, you don't walk, you float!"
Finally, Dr. Bombay returns with the antidote for the antidote and Sam is back to normal. And Mr. Prescott likes the slogan.