[Starring] William Shatner as Captain Kirk, Leonard Nimoy as Mr Spock

This week: The Enemy Within
The intrepid captain of the USS Enterprise is usually more than a match for any adversary, but better men than he have been worsted by their worst impulses, when a malfunction of the transporter causes his alter ego to take shape, it's quite an encounter, with more than the fate of his better self in the balance.