Max tries on an engagement ring not realizing that it is actually the Morris Diamond.
Fabulous jewel worth $275,000 which the KAOS League of Bald-Headed Men plans to steal from Spiegle's Jewelry Store and smuggle out of the country.
The plot is temporarily thwarted when Maxwell Smart arrives in the store to buy an engagement ring for 99. To prevent the diamond from falling into the hands of the KAOS agents, Mr. Spiegle sells the ring on which it is mounted to Max for just $80.00.
This initially causes trouble for Max when he is accused of stealing government secrets to pay for it. However, upon returning to the store with 99 and the Chief, his story is verified and he returns the ring to two men who claim that Spiegle was "going through some sort of a breakdown."
Too late, the Chief recognizes them as Winters and Sommers, members of the League.
The Morris Diamond is finally recovered at a bowling alley where the Bald-Headed Men are receiving the stolen gems and hiding them under their toupees.
[Episode #91: "Diamonds Are a Spy's Best Friend".]