3x28 - Bonanza

Adam is left to die in the desert after two thieves take $5,000 and his horse from him. Near death, he stumbles into an old prospector named Kane who offers to lend him a mule and supplies in exchange for three day's work at his mine. Kane, however, turns out to be a demented madman. He holds Adam prisoner and tortures him to prove his theory that anyone could be driven to kill, even a man as rational as Adam. This is Pernell Robert's favorite episode along with "The Wooing Of Abigail Jones".