After Bones accidentally injects himself with a shot that causes him to have dementia, he jumps into a time-travel gateway and lands in New York in the 1930's. Kirk and Spock must go in after him and prevent him from doing something in the past that could alter the future. Kirk finds a love interest, played by Joan Collins, but comes to find out that she will play a key role in determining the outcome of Earth's future. Without spoiling it, lets just say it appears Kirk will never have a steady love relationship as long as he is captain. Great job by Shatner and leaves you numb at the end. He even uses the word "hell', which was probably a big deal on television in the late 60's.