Star Trek - The Original Series, Vol. 38 - Episodes 75 & 76: The Way to Eden /  Requiem for Methuselah
"The Way to Eden," Ep. 75 - Kirk and crew must deal with the insane leader of a band of rebellious idealists who are searching for the fabled planet Eden. " Requiem for Methuselah," Ep. 76 - An outbreak of Rigellian fever aboard the U.S.S. Enterprise forces Kirk to find an antidote on Holberg 917-G, where he meets the mysterious genius Flint.