A Prime Directive issue becomes a lively comic piece when the landing party beams down to a planet to correct the social damage inflicted upon the culture, which is based on the Chicago gangsters of the 1920s because of a single book left behind by a Federation starship a century before.
Unfortunately, after beaming down, Kirk & Co. constantly find themselves on the business end of several machine guns, in the middle of the war between leading gangsters Bela Oxmyx (Anthony Caruso) and Jojo Krako (Victor Tayback), who both want a supply of Kirk's "heaters" (phasers).
The running gag of Kirk and Spock getting guns pulled on them proves quite amusing; every time it looks like they've gained the upper hand, ka-chack—two more goons with guns. Meanwhile, we get to see Kirk and Spock in gangster suits, a hilarious game of "Fizzbin," Spock saying "Check!", and Kirk in full role-playing mode, chewing the scenery in some genuinely funny scenes as he tries to work out everybody's piece of the action. It's an enjoyable gem with sharp dialog and good timing, as well as an undercurrent that still manages to say something relevant about intervening in other societies.