The Double Affair - S1.E8

THRUSH creates a double for Solo, and with the seductive aid of Serena (Senta Berger), Darius Two (Michael Evans) kidnaps Solo and substitutes the phony into U.N.C.L.E.'s efforts to transport the code to a secret new weapon. Illya and stewardess Sandy Wister (Sharon Farrell) eventually realize a switch has been made, and the real Solo escapes and in a climactic scene battles "himself".