His ears were caught in an automated rice-picker.
Sure enough, the finale is TCOTEOF (The City on the Edge of Forever) written by Harlan Ellison. This one has it all: time travel, romance, angst, lunatics, war, humour and a sexy chick. It is probably the most intelligently written script ever penned for Star Trek, though poor Harlan had to go through quite a trial to get his finished product on the screen.
The sexy chick is a social worker (Edith Keeler) who tries to set up a peace movement, then Kirk falls in love with her, tragedy happens and everything is back to normal at the end except for a heart-trodden JT Kirk. Joan Collins is wonderful in the role of the innocent do-gooder and how she ended up her career playing harpies and tramps is beyond me. Personally, my favourite role of hers is as the sleazy realtor in the b-movie, Empire of the Ants.