Elaine is dating jazz saxophonist John Jermaine, but complains to Jerry that John does not give her oral sex. Jerry meets Clyde, one of John's bandmates, and describes the relationship to him as "hot and heavy". When Elaine learns of this, she becomes upset with Jerry, fearing that the phrase made her seem more invested in the relationship than John might be comfortable with. At a concert, John and his band perform a new song entitled "Hot and Heavy", embarrassing Elaine.
George's parents Frank and Estelle meet his fiancée Susan's parents for the first time at the Ross apartment. Frank brings a loaf of marble rye bread. After an uncomfortable dinner, Frank takes the rye back home because the Rosses did not serve it. Fearing this incident may create a rift between the families, George plans to sneak an identical loaf of bread into the Rosses' kitchen to create the illusion that the bread was simply misplaced. He plots to send Mr. & Mrs. Ross on a hansom cab ride (driven by Kramer, who is picking up the usual driver's mail) as a wedding anniversary present, while he and Jerry sneak in the bread. At the bakery, Mabel gets the last marble rye. After trying unsuccessfully to get it from her with bribery and appeals to sympathy, Jerry robs it from the elderly woman.
Kramer, having overbought at the warehouse club, feeds Rusty the horse "Beef-a-reeno" which makes him flatulent. Rusty farts so much the Rosses cut their cab trip short, preventing Jerry from entering the Ross apartment. After trying unsuccessfully to toss the bread up to George at the third floor window, Jerry hooks it to a fishing pole George found in the apartment. George reels the rye bread up, but the Rosses catch him.
Elaine explains to John that she never called their relationship "hot and heavy". John, however, tells her that he was happy with the idea of being "hot and heavy" with her, and offers to give her oral sex. After overexerting in the bedroom, he cannot make a note during a showcase for record producers, producing a series of off-key whistles instead. Embarrassed, Elaine leaves the show.