A defecting Thrush scientist informs Waverly of a Thrush poison gas project. NS and IK are sent to destroy the Thrush base in the desert. The scientist, however, flees UNCLE's care to try and get his son back from a Thrush-run boarding school in Switzerland. Big mistake. Rest of the plot concerns UNCLE and Thrush's attempts to get the boy, played by one-time Dennis the Menace Jay North.
Guest star: Angela Lansbury (Effie Van Donck), Jay North (Bartlett Warshowsky), Diane McBain (Joanna), Arnold Moss (Noubar Telemakian), John Hoyt (Head), Gil Perkins (Dr. Boris Warshowsky), Ernest Winters (Basil), Christopher Essay (Steward), Gloria Neil (Sarah)
First aired: 12 November 1965
Sorry, I only have a few episodes of s2 and s3 but all of s4.
I'll being putting up what I have in order. :)