Season 3, Episode 23 (March 11, 1975). Written by Dennis Koenig; Directed by Gene Reynolds.
One of the most-cited early M*A*S*H episodes, "White Gold" is built around a single absurd medical dilemma: penicillin has become more valuable than money at the 4077th, and Colonel Flagg (Edward Winter) is on his way to investigate the black market in the drug. With Frank Burns in possession of a huge surplus supply of the stuff—hidden in everything from the brim of his hat to a jar of maraschino cherries—the surgeons are desperate to get it out of his hands before Flagg arrives and starts asking questions [1][2].
The episode gave Linville one of his best Burns showcases: the discovery of Frank's penicillin obsession is the kind of grotesque comedy the early show did better than almost anything on television. Radar, Hawkeye, and Trapper scheme to liberate the drug, while Margaret Houlihan's surgical goldfish ("Captain Wildcat") keeps getting dosed with the surplus [1].
It is also the first proper Colonel Flagg episode after "A Smattering of Intelligence" introduced the character at the end of Season 2. As the MASH4077TV episode guide notes, Flagg "allows thieves to get away with the 4077th's supply of penicillin, regardless of the fact that the drug helps save countless lives. Flagg needs to use the drugs to get information from the North Koreans." Hawkeye and Trapper then turn the tables on him by tricking him into believing he has appendicitis, so they'll have to keep the penicillin in case he needs emergency surgery [2]. Winter's performance is already a finely tuned engine of menace and self-importance—he arrives at the 4077th as a fully formed nemesis, complete with code names, accusations, and an unsettling willingness to physically threaten the staff. The 4077th's repeated narrow escapes from his investigation establish the formula the show would return to every time Flagg showed up for the rest of the run [3].
The episode aired a week before "Abyssinia, Henry," and both are widely considered among the strongest installments of the early Trapper John era.
[1] White Gold (M*A*S*H) - Wikipedia [2] M*A*S*H Episode Guide - MASH4077TV [3] List of M*A*S*H characters - Wikipedia