S1·E15 The Human Touch

Arguably the finest episode of the series, featuring guest star Peter Lorre as an ex-con criminal mastermind determined to wreak revenge on master criminologist Sebastian Cabot. An intricate series of cat and mouse moves between the two geniuses culminates in a surprise and ultimately poignant ending, befitting the episode title. This episode stresses the close friendships between the three detectives of CHECKMATE INCORPORATED as it contrasts with that of the brilliant, but soulless Lorre. Directing, writing and acting are all exemplary.