The Affair is presumed to be taking place in the Austrian Alps, however when you first see the domed building where THRUSH is holding the real Solo, it is actually the Griffith Park Observatory in Los Angeles California. A good portion of the show is filmed in Griffith Park (all the winding roads and cliffs).
This was the first episode without the introductory sequence where Solo, Kuryakin, and Waverly introduce themselves and explain what they do.
In an unusual move, Senta Berger is shown in the opening credits between David McCallum and Leo G. Carroll. Normally, all guest stars are introduced after Carroll.
This episode where shot with the intention of making The Spy with My Face (1965) a foreign theatrical film, and in the '80s available on videocassette and, now, DVD.