In the "Star Trek" episode "The Empath" (December 6, 1968), Captain Kirk (William Shatner), Spock (Leonard Nimoy), and Dr. McCoy (DeForest Kelley) are on an away mission when they are abruptly kidnapped by off-screen aliens and deposited in a mysterious, blackened chamber somewhere beneath the planet's surface. While trapped, they encounter a mute woman in purple whom McCoy names Gem (Kathryn Hays). Gem, they find, has an extraordinary superpower. When someone is injured, Gem can heal them by absorbing their wounds into herself. She feels an equal amount of pain. The wound is then healed rapidly.
Gem ends up having plenty of opportunities to use her superpowers as the four characters are repeatedly tortured by evil, large-skulled aliens called Vians (played by Alan Bergmann and Willard Sage). The Vians spend the bulk of the episode tormenting and injuring the Enterprise crew members, sometimes while Gem watches. Gem, meanwhile, offers to heal them each time, becoming weaker and weaker with each healing.
The Vians eventually reveal their reason for their actions. It seems that Gem's species is about to become extinct thanks to an impending supernova. The Vians can save either her world or another populated world nearby, but don't have the resources for both. The Vians say they will only save Gem's world if she proves that she is willing to sacrifice her own life (that is, by healing someone who's near death), thereby passing a twisted morality test.
It seems the BBC had second thoughts upon gearing up to air "The Empath" for the public in 1970. The broadcaster had already received a number of complaints about "Star Trek" because of some of its rougher material, and an episode about torture, it knew, was definitely going to just keep the angry letters coming. "The Empath," along with three other episodes of "Star Trek," were thusly struck from the BBC's broadcast schedule entirely and left off for literal decades. Ultimately, "The Empath" didn't air in the UK until the '90s.