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

Writer: Jean Lisette Aroeste
Dir.: Ralph Semensky

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 Chapel: Majel Barret
Dr. Miranda Jones: Diana Muldauer
Lawrence Marvick: David Frankham

Stardate 5630.7

Dr. Miranda Jones beams on board with a container. She is accompanying Kolos, the ambassador of the Medusans. For this occasion Spock wears the symbol of a Vulcan philosophy: The infinite combination of infinite diversities. When even the most diverse appearing beings, inner states of mind, the most different entities or groups of peoples, the most different experiences or findings are combined – as they are – to achieve the good, it will pierce in brilliancy. Infinite Diversities in Infinite Combinations = The IDIC. 

Being partly telepathic Dr. Jones can communicate with the Medusan and she is obviously very fond of the being, who consists of various patterns of light, frequences and energy, who leaves anybody seeing him mentally insane. Not by intention, but simply because it is too much for anybody to comprehend or too much to make surviving possible after having seen him. The Medusans are highly effective in navigating and mental abilities. Highly interested in making contact, Mr. Spock is attracted to the Medusan and his escort, Miranda Jones. In Dr. Jone’s company is Lawrence Marvick, who had a big part in designing the Enterprise's engines. Marvick loves Dr. Jones, who only has eyes for the Medusan. 

Eyes – Dr. Jones is blind and can "see" by the devices built into her clothing. That way she can open the box, where the Medusan is, without any danger and the devices help her by (e. g.) telling her the exact distance from herself to the wall or the tallness of a person. During dinner Dr. Jones suddenly experiences a warning. She shares that she had the notion that someone plans a murder ... and she is correct. Marvick is envious in the Medusan and plans to kill him. But it is him who gets insane and dies after he's opened the Medusan's box. Before he dies from the madness, he enters the machine room and – in his madness –steers the ship into another dimension. Too late he is overwhelmed and dies soon. No one is able to get the ship back out of that dimension, except the Medusan who is an expert in navigation. 

It is agreed upon one solution: Spock will put on protective glasses, so that he cannot see all of the Medusan, and mindmeld with him. By this he (Spock/ Kolos) would navigate the ship out of danger. Dr. Jones ojects to this solution. She says she's more qualified to share Kolos' mind, because she she knows him intimately, but Kirk and Spock counter that she knows nothing about navigation and might do not be able to carry on the Medusan's thought properly. The woman must abide to Kirk's decision, but she's clearly upset by that and does not hide her disappointment.  

The protective box is shielded on the bridge. Spock puts the glasses on and goes behind shield–walls to engage in a mindmeld with Kolos. When he emerges from there, he has a friendly word for everybody, smiles at Miranda and takes over the navigation. He quotes poetry to Uhura, which makes Dr. McCoy comment "This is not Spock!" Immediately Spock retorts "Do you not believe I can know Byron?" And McCoy sighs "THIS is Spock!" The ship in safety, Spock/Kolos goes back to end the mindmeld. Telepathically Miranda makes Spock forget his protective glasses, because she is envious that he could see Kolos – something she'll never will be able to do, even with protective glasses. When Kirk sees the visor lying on Spock’s desk, tries to warn him, but it is too late: Spock goes insane and attacks the bridge officers. 

Sedated, he lies in sickbay and is bound to die soon, because Miranda says she cannot do anything. Kirk confronts her, knowing she'd been envious that Spock had greater telepathic abilities and has seen Kolos. Making her aware of the consequence, he leaves her alone with him and she changes her mind. Miranda mindmelds with Spock and helps to regain normality sharing with him what she has learned from the Medusans so far. It is a hard experience for her, but, through it, Miranda will finally find peace. When she leaves the Enterprise, she salutes Spock telling him "I understand, now, Mr. Spock. The glory of creation is in the infinite diversity." And he replies "And in the way our differences combine to create meaning and beauty."