At Arnold's, Joanie and Chachi (as well as several other couples), finish up a slow dance. After the song has ended, they continue to dance. He says to Al that there's a song in his heart to which Al replies that there's a health inspector in his kitchen. He says he found something in the soup - Clarence. Chachi tells Joanie that it's the fourth anniversary of the day he first asked her out. They kiss. Jenny runs in and says that she and Joanie have to talk. Chachi goes into the kitchen. Joanie and Jenny sit down, and Jenny says that "it" has finally arrived. She sent away for a product in an advertisement that read "Are you a bust in the bust?" Jenny wants Joanie to go the Post Office to pick up the package because she put Joanie's name on it. Joanie is mad at first, but Jenny says it's in a plain, brown wrapper. They head toward the exit as Howard and Marion come in. They've come for Al so that they can go bowling.
At the house, the package sits on the kitchen table. Jenny is excited about what the Ajax Bust Builder might do for her, but she, also, doesn't take disappointment well. Joanie tells her that she's got nothing to lose. Howard and Marion come in the front door exclaiming that they've won, but nobody is there to hear them. Joanie and Jenny come in from the kitchen giggling. Joanie says they were just finishing up some milk. Howard and Marion exclaim again that they've won. Howard says that Marion was sensational, and it's all due to a new approach he showed her. She demonstrates her form, and her back ends up going out. Jenny tries to help by yelling "boo!," so Marion tells her to go home.
Later on, Roger and Potsie finish hanging Marion up on the door between the living room and the kitchen. Roger says it should stretch and relieve the pressure. Potsie says the apparatus is his and that his father used to hang him up with it. Roger says that's pathetic, and Potsie replies that it's better than being rolled up in the rug. Roger and Potsie have to leave, but Roger tells Marion to holler if she needs anything because Joanie's upstairs. Potsie starts smiling and says that he remembers the time when his father put him in an old tire and rolled him down a hill. They leave. Fonzie comes in the front door looking for Marion. He finds her hanging on the door. Marion feels badly because Howard really wanted to win the bowling trophy. Howard comes in and says he thinks he's found a new partner. Her name is Fern Flagg and she's an assistant loan officer at the bank. Fonzie knows of her. He talks to Howard privately and tells him about the stories going around about her. He criticizes Howard for lying about her appearance. He told Marion that she was an old spinster woman, but Fonzie says she's a knockout. Fonzie leaves and says that Howard and Marion can talk about anything they'd like such as the truth. He opens the door, and Fern is standing there just about to ring the bell. Howard introduces Fern to Fonzie. Fern offers Howard a lift to the bowling alley. Howard introduces Fern to Marion, and Marion gets a concerned look on her face. Howard tells Fonzie to let Marion down in an hour. Howard and Fern leave. Marion talks to Fonzie about Fern. She is furious that Howard has lied to her. Marion says she doesn't want Fonzie to see her cry, so he pushes the door closed.
Later on, Joanie and Jenny come in an open the package. All that's included is tissue. Jenny thinks it must be just packing material, so she reads the instructions. They say to roll the tissue into balls and place in undergarment. Jenny is upset that she spent $12.99 on tissue but suggests they wrap it back up, and sell it to her sister. They leave via the kitchen door. Howard and Fern come in the front door, and Howard tells a hardware joke. Fern says she hasn't laughed this hard in years. Howard says he better wake Marion to tell her that they won the mixed-doubles. Fern says that Marion needs her rest. Fern comes on to Howard by complimenting him. He says he was a shot-putter in high school, and she says that's her favorite sport. He demonstrates his shot-put form with a bowling ball. She asks what he does to keep so fit. He lies about running and doing push-ups. Howard asks Fern if she'd like to go to the award banquet with him since Marion can't go. She accepts. Fern leaves and thanks Howard for a wonderful and exciting evening. She calls him "champ," and Howard says he'll see her to her car. Marion comes down the stairs, and Fonzie comes in through the kitchen with some dinner. Marion says she heard everything Howard and Fern said. She said he used all of the same things on Fern that he used on Marion to impress her. Fonzie tells Marion to confront Howard.
At the banquet, Howard and Fern sit at a table. They're the last ones there. Howard says that he can keep the trophy the first week, and she can keep it the second. Fern says that when she has it, he can come visit it. Howard says it's the first trophy he's ever won and confesses to Fern that he never really was very athletic. Fern says that, push-ups or no push-ups, he's man enough for her. She tells him that she wants them to be more than friends. She suggests they take the trophy to her place right then. Howard says he shouldn't and won't. He says he's a married man, and his family means everything to him. Marion peeks in from behind a curtain with binoculars. Howard excuses himself to give Marion a call to see how she's doing. Marion approaches Fern and tells her that she was consumed with jealousy. Fern says that she was, indeed, after Howard. Marion calls her a tramp. Fern apologizes saying that she didn't mean to cause any harm. She leaves.
Howard comes back into the room. Marion says she wishes she had gotten there sooner reasoning that she probably missed all of the fun. Howard says there wasn't any fun because Marion didn't get there sooner. He tells her that he loves her. Marion says that she trusted him with Fern, but, the next day, they're changing banks.