Spock's court-martial board views the video stream from Talos IV of Captain Pike's imprisonment 13 years earlier and of the Enterprise's attempts to rescue him. The Talosians, using their powers of mind-reading and illusion, place Pike in worlds from both his memory and his imagination. The one constant is Vina, the beautiful blonde survivor of a crashed Earth ship (the other half of a Talosian plan for a captive Adam and Eve). Number One's attempts to liberate Pike result in her and Yeoman Colt's capture (additional breeding stock for the Talosian plan), but when the humans and Talosians learn more of each other, the situation takes a turn neither side expects. As the Enterprise approaches Talos IV once again, Kirk and the court watch the past unfold and learn the real reason for Spock's mutiny. Written by
Did You Know?
In the script, McCoy and Scott have a scene wherein they explain to Kirk how they figured out which computer bank Spock tampered with to lock the ship on course. They took perspiration readings on all banks, and since Spock's sweat has copper in it, traces of copper were found. This scene isn't seen in the episode. See more
At the end Pike and Vina are shown entering the narrow opening of the elevator shaft. Pike, who is shown in his normal form before his accident, was in fact still confined to his medical chair. The chair was earlier shown to be overly big and bulky, and would not have fit through the narrow opening of the elevator. See more
Their power of illusion is so great, we can't be sure of anything we do or anything we see.
Edited from Star Trek: The Cage