Episode 2 Inhibitions broadcast Jan 14th 1967
On missiondate 204.2, the Commonwealth starship CSS Endeavour, arrives in orbit around the dying planet I187 , in order to observe and document the planet's break up. A landing team is also beamed down to the research station based on the planet in order to discover what has happened to the team of scientists who were stationed there, but who have not been heard from for months. The team is confused to find that all six of the scientists have died for no readily apparent reason. They are found in a number of bizarre positions - one man apparently in the middle of taking a shower fully clothed, and another having seemingly just sat at his desk until freezing to death - and all life support systems have been shut down and the controls frozen solid.
One of the Endeavour crewmen, Alan Stein, removes his glove while examining the station, and is contaminated by a strange red liquid. When Lt. Stein and Science Officer Spock return to the ship they are given a clean bill of health by Chief Medical Officer Dr. Noyce, but Stein notices a strange itch on his hands, and begins to act irrationally. After yelling that human space exploration is actually doing more harm than good, he threatens Lieutenant Chekov and CPO O’Gorman with a knife, then attempts to turn it on himself. He suffers a minor wound, but is stopped and escorted to the Medical Centre Dr. Noyce is then left bewildered when Stein inexplicably lapses into catatonia.
Soon, Stein’s affliction begins to affect other crew members and quickly spreads throughout the ship. They each begin to display both comical and horrific exaggerations of character, revealing things about themselves which they would have usually kept secret.
As the affliction spreads, Chekov abandons his post on the bridge and begins acting like an 18th-century sword-fighter, running around the ship and challenging everyone to a duel. Ship's Engineer CPO Aedh O’Gorman, who believes himself to be descended from Irish royalty, wanders down to Engineering where he tricks the staff into leaving and takes over control of the ship, declaring himself the Captain of the Endeavour, before giving orders and warbling inane songs repeatedly over the public address system. The Endeavour starts to drift out of control and slowly falls out of orbit, pulled down by the erratic gravity of I187.
Noyce and Spock manage to avoid the affliction and find that the water on I187 has a complex chain of molecules, which, once in the bloodstream, affects people in a similar way to alcohol, depressing the centers of judgment and self-control. They find that eventually the molecules break down with no residual effects worse than a mild headache.
Chekov charges into the ship's bridge and threatens Pike and Braun's lives but he is finally stripped of his sword and rendered unconscious by Pike. Meanwhile, O’Gorman is stopped and control of Engineering is regained. However, O’Gorman has turned the engines off and Chief Engineer Scott tells Pike that there is not enough time to get them started again before the Endeavour is dragged down by I187's break up.
To avoid crashing into the planet, Captain Pike orders a highly dangerous attempt at a full-power restart, using the Jump Engines to start the ship's warp engines by creating a "controlled implosion". Spock warns that this is possible in theory but that it has never been tested before.
The warp engines start and the Endeavour reaches the Jump point. However the effect of using the Jump Engines to start the warp engines and the gravitational effects of the break up of the planet cause a malfunction in the Jump Engines. When they arrive at Earth, they receive a signal that is announcing the “I have a dream” speech of Martin Luther King.