Sulu is poisoned whilst visiting the planet Phylos, but his life is saved by the inhabitants. The Phylosians worship the giant clone of a human from the 20th century, Dr. Starros Keniclius. Determined to enforce galactic peace, Keniclius abducts Spock and clones him also so that the giant can act as a peacemaker. Left dying by the cloning process, Spock has only one chance - a mind meld from his giant clone. But can Kirk talk clone-Spock and Keniclius around?
Oh dear. The idea that somebody wants to create a race of giant Spocks in order to force peace on the Federation, an organisation which is devoted to peace anyway... the absurdity of it simply drowns out any kind of point the episode is trying to make.