This one was from a show called Insight, and the episode, called The Day God Diedhad a group of the regular Trek guest stars on it: Mark Lenard, Diana Muldaur, Mariette Hartley. In addition, it had names like Carroll O'Connor, Lloyd Bochner, Beverly Garland, etc.
I can't follow everything tonight owing to chronic nervous system stuff, but that's a great cast.