For much of this episode, it feels like one of those rather less compelling late 1950's-early 1960's detective shows; but it's actually better than that. The reasons are:
For one thing, it features the stunningly beautiful Karen Steele. This series had, in this viewer's opinion, hands down, a greater number of very attractive women guest stars, than any other show that was ever on TV! Including, say, Star Trek or Baywatch! Plus, the women are always wearing those great, stylish and flattering clothes of that period.
Next, there are fine supporting performances from John Banner and the lady playing his wife. Viewers will know John Banner from his many years as the hearty, comic sergeant on Hogan's Heroes. Here, we see him in a very different role, as a thoughtful, kindly, understated businessman. We get to see what a fine actor he was.
Finally, the plot of the story ends in a very interesting and unusual way; a way that was very untypical for TV of its time, and which in fact would still be untypical today. Big points to the scriptwriters for that. All in all, this is another very watchable outing of this fine series.
Sure, for Antwerp, we get the Warners backlot, plus some establishing shots of Antwerp. Frankly, even now, we'd be very lucky to get more than that in any episodic TV series meant for American viewers. To me, that's no big deal.
Viewers should know, this episode is all Stu! We get a very brief scene in which Roger Smith appears, but the rest of the regular cast does not appear in this adventure. While I am very fond of all members of our regular team, I also appreciate those episodes where we get something different, and I especially like the ones which are set in some foreign country: in Europe, or Mexico, or wherever. When you think about it, this series had a really extensive regular cast: the three detectives, and the lovely French secretary, and Roscoe, and then the new car valet guy too for some shows.