A Piece of the Action

The Horizon visited the planet Iotia a hundred years ago, long before the Prime Directive forbid interference in pre-warp alien cultures. Beaming down to investigate the damage, Kirk, Spock and McCoy discover a culture run by mobsters! It seems that Horizon left behind a book, "Chicago Mobs of the Twenties", and the highly imitative people of Iotia patterned their society after the groups described in its pages.

Synopsis adapted from TVmaze (CC BY-SA 4.0)