Executive Producer: Gene Roddenberry
Producers: Gene L. Coon + John Meredyth Lucas
Associate Producer: Robert H. Justman
Script Consultant: D. C. Fontana

Story by: David P. Harmon
Writers: David P. Harmon and Gene L. Coon
Dir.: James Komack

Captain Kirk: William Shatner
Science Officer, First Officer, Cmdr. Spock: Leonard Nimoy
Dr. Leonard "Bones" Mc Coy: DeForest Kelly
Lt. Sulu: George Takei
Lieutenant Commander Montgomery Scott: James Doohan
Lieutenant Uhura: Nichelle Nichols
Nurse Christine Chapel: Majel Barrett

Bela Oxmyx: Anthony Caruso
Jojo Krako: Vic Tayback

Stardate: 4598.0

The landing party of the U. S. S. Enterprise, Kirk, Spock and McCoy, about to meet the representatives on Iotia, are encountered by a gang -like environment of the old - Chicago - gangster - times. The planet has been visited by the U. S. S. Horizon a hundred years ago and it is known that the Iotians are highly imitative people. They wanted to visit one of the planet's people in charge to renew contacts and are facing guns instead. Bela Oxymyx wants to take over the whole planet with the help of the advanced weapons from the Enterprise.

Oxymyx shows them "the book", a book (Chicago Mobs of the Twenties) telling about the conditions of life in Chicago at the times of the gangs, and tells them that they live it as closely as possible. Kirk quickly adjusts to the slang of the time, and Spock tries, too. Spock also handles a heater (a machine gun). They are locked up to prevent the rival gang leaders to take advantage of them. This is exactly what Jojo Krako and the other gang leaders intended. While their guards play cards, Kirk introduces a new game to them (knowing they love to imitate) and invents several special rules like: "This card is higher than that - but only on Tuesdays" Intrigued they watch the cards and are rendered unconsciousness by neckpinches. The trio escapes.

On their way to the other leaders Kirk "drives" a vintage car. The others care that the incident is not repeated. Kirk and Spock in suits and hats of the time by now together with McCoy get a help of a boy, who wants a piece of the action. Accepting the rules, the language and the living conditions they met, they arrange for an alliance amongst the most influential leaders with the help of a little demonstration: Outside the place they meet a phaser beam from the Enterprise leaves all gangsters on the street unconscious. This convincing incident gives Kirk full attention of all of the leaders and outs him into the position to get his suggestion of a world government headed by Oxymyx and shares for all the others through. The Federation will visit Iotia annually and get their "piece of the action".