This one is all Stu, and he does a fine job of probing the murky world of espionage in early 1960's Vienna. Of course, the good old Warner Brothers backlot stands in for Vienna, but that doesn't detract from the episode. Some European autos are used, fittingly, which helps with atmosphere.
What really makes this episode stand out, is how good the supporting cast is. They are all very good, and that is a big help to our man Stu, giving him a basis for some strong interactions. Another good point about this episode, is that the direction is really first-rate; the story never drags but moves along at a quick and exciting pace.
My favorite episodes are always going to be the ones set in and around the L. A. office, where we get to see all of the fine regular cast interacting and bantering, but an outing such as this makes a very enjoyable change of pace. Some episodes of this series have some humorous aspects, often with Cookie and his witticisms and girl-chasing; we don't get any of that here, as Stu is off in Vienna for nearly the whole show, just having a quick opening scene in the L. A. office.
The backstory to Season Five, of which this episode is a part, is that the ratings of the series were starting to decline, which resulted in the radical and disastrous changes to the series in Season Six, which was truncated, as the series was cancelled after 20 Season Six episodes.
But this one is well worth watching.