Let That Be Your Last Battlefield" is the fourteenth episode of the third season of Star Trek: The Original Series. It was first broadcast January 10, 1969, and repeated August 12, 1969. It was written by Oliver Crawford, based on a story by Gene L. Coon (writing under his pen name "Lee Cronin") and directed by Jud Taylor. The script evolved from an outline by Barry Trivers for a possible first season episode called A Portrait in Black and White. The script was accepted for the third season following budget cuts. The episode guest-stars Lou Antonio and Frank Gorshin, best known for his role as The Riddler in the Batman live-action television series. Gorshin received an Emmy nomination for his portrayal of Bele.
On stardate 5730.2, the Enterprise is on a mission to help decontaminate the polluted atmosphere of the planet Ariannus when sensors track a Federation shuttlecraft reported stolen from Starbase 4. The craft is disabled and brought aboard along with its strange alien pilot who is found injured and taken to sickbay. The man later awakens and identifies himself as Lokai — a political refugee from the planet Cheron who requests asylum. Lokai's most striking feature is that his skin is half black and half white, the two halves split perfectly down the center of his body. His unique physiology is explained by Mr. Spock as possibly being "one of a kind".
Shortly thereafter, sensors detect another spacecraft in fast pursuit of the Enterprise. Curiously, the craft remains invisible to all but sensors and sets itself on a direct collision course with the ship. Moments later, Spock reports the invisible craft has disintegrated and deposited an "alien presence" aboard the ship. Kirk turns to see the alien pilot who has beamed himself directly to the bridge. The second alien identifies himself as Bele.
Like Lokai, Bele is half black and half white, with the color divided by a line through the exact center of his face. However, the sides of Bele's black and white skin are reversed from those of Lokai, a difference which seems inconsequential to the Enterprise crew but of great importance to Bele, Lokai, and, apparently, their civilization. The difference is pointed out by Bele to a perplexed Captain Kirk who asks what is the difference between them, to which he replies, "Isn't it obvious? Lokai is white on the right side. All his people are white on the right side."