Executive producer: Gene Roddenberry
Associate producers: Edward K. Milkis and Gregg Peters
Producer Fred Freiberger
Co-producer: Robert H. Justman
Story consultant: Arthur H. Singer

Story by: Lee Cronin (Gene L. Coon)
Writer: Oliver Crawford
Dir.: Jud Taylor

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
Ensign Chekov: Walter Koenig
Nurse Chapel: Majel Barret
Lokai: Lou Antonio
Bele: Frank Gorshin

Stardate 5730.2

The Enterprise comes across a stolen shuttleThey rescue the man on board. While examining him, they wonder about his unusual look - he's black on a side and white on the other. Spock and McCoy agree that it must be the result of a genetic mutation. When the man comes around he says his name is Lokai and he's from Cheron planet. Soon after a high speed ship is detected by sensors, but the Enterprise crew is unable to see it. The invisible ship points straight on the Enterprise and, just when it is about to collide it is destroyed, but someone materializes on board - Bele, Cheron's chief officer. He too is white on one side and black on the other half. 

Bele claims Lokai is a traitor and wants to arrest him. Lokai claims he's unjustly pursued because of his race. He accuses Bele and all his people of slavery and genocide against his own and seeks asylum. Bele insists to have Lokai consigned in his custody and demands that the Enterprise bring him and his prisoner back to Chevron. Kirk states that he has a mission to perform and after that he will hand them both to Federation Authorities. Bele his not satisfied and uses his mental powers to get control of the ship and set course to Chevron. 

Kirk manages to regain control of his ship by initiating the self-destruction sequence and defying Bele to maintain control of the Enterprise and die or give the command back to him and have the sequence stopped. Bele gives in and Kirk, accepting his surrender, tries to teach both his guests some values of freedom and democracy, by allowing them to wander freely around the ship. 

Spock hears Lokai talking some crewmembers into his cause of resistance against oppression. Later, during a meal, he and Captain Kirk listen to Bele who's trying to convince them of Lokai's race inferiority. Spock says they appear to be of the same race. Shocked Bele answers him that it is obvious: He himself is black on the right side, and white on the left side, while Lokai and his people are white on the right side and black on the left one. 

After he has carried out his mission, Captain Kirk orders the Enterprise back to the Star Base, where he's willing to unload his guests, but the ship is again out of his control and heading to Chevron. This time Bele has used his powers to burn both self-destruction and navigation control. Bele continues to pursue Lokai even when they reach their home planet. Spock has found out that all is dead on the planet. All have killed each other. Bele and Lokai balme each other's people for the destruction and fly down to the planet surface to continue their fight.