This was an entertaining episode, well played out by a great cast. Kathy Brown was great, and Kirk could easily fall for her. The idea, though, was first used in the H. G. Wells short story, "The New Accelerator," published in 1901 in the Strand magazine. Well's story was later adapted into the 1966 Wild Wild West episode, "Night of the Burning Diamond" written by Ken Kolb, two years before the Star Trek episode. I liked all of them. Dr. McCoy and Spock came up with the ideal solution to Kirk's disappearance and how to bring him back. The ending was bittersweet, as were so many episodes in which Kirk fell for a woman (or android).