2-24: The Ultimate Computer
The Enterprise's test of Dr. Daystrom's greatly enhanced computer becomes deadly.
2-20: Return to Tomorrow
Several crew members are possessed by advanced non-corporeal beings.
2-04: Mirror, Mirror
A transporter accident swaps Kirk, McCoy, Scotty, and Uhura from distinctly opposite parallel universes.
2-17: A Piece of the Action
Enterprise discovers a gangster-run planet similar to 1930s Earth.