 In Star Trek s penultimate episode, Kirk, Spock, and McCoy find themselves transporting down to the planet Sarpeidon to investigate (and possibly aid) a planet s evacuation before its sun can go nova. All they find, however, is a single librarian, Mr Atoz, tending a collection of unusual discs, which play the planet s history and (to their surprise) allow their users to travel into the past. McCoy and Spock find themselves locked in the planet s ice age; Kirk in the planet s colonial age; and they must escape back into the present before the sun explodes, and the library s computer is destroyed. To complicate things, Spock finds himself attracted to a beautiful political prisoner named Zarabeth.