This is the episode that starts the fourth series of TMFU, often called more serious than the preceding one, which may have overdone the camp & slapstick slightly.
My personal feeling is that the larger-than-life elements of the last series are not completely missing here. Not the least eccentric thing about this episode is the agent Harry Beldon, played by Albert Dekker. I love his characterisation of his frankly ridiculous character enormously. I was even more surprised to look up Dekker & find the cause of his death was auto-erotic asphyxiation! Beldon is so far from the image of what a secret agent should be, that I think it is impossible to deny the high camp element of this series. His character is almost - I'm finding it difficult to find the right word - a spoof rather than caricature of the whole spy genre, Avengers, Bond, & everyone, from the moment he gets out of the car drinking champagne.
To my mind this caricature of the spy genre is made more crashingly obvious by the fact that the murder weapon is an UNCLE Zeron Acturator - merely being shot with an UNCLE-issue revolver would be slightly pedestrian in comparison to inventing a weapon that is the *only* one that could do the injury. The champagne-drinking was an Avengers touch, but the invention of a fantastical weapon suggests that it is firmly Bond being spoofed here. I suppose it is a plot point rather than a weakness, but once again UNCLE's security is shown up to be something of a shambles: it is almost a caricature of the spy genre & an inversion of it at the same time. Here the world of the spy has become so self-referential that in this episode nothing outside of UNCLE's inner workings come into it, even the threatened Thrush takeover is really only important as it affects UNCLE. UNCLE is the point, UNCLE is the threat, UNCLE is the vulnerable object here. Frankly, if a world-wide security organisation is so vulnerable that a world-wide takeover can be masterminded from inside, it isn't up to much & heads should roll. Any organisation where one operative can say 'Gentlemen, you seem to forget that I am UNCLE North-East,' stands or falls by the integrity of that operative.
Yet this episode manages to hold attention, by a mixture of good visuals, good characterisation & a developed plot building on many of the standard pieces of the spy genre, such as rendez-vous which becomes an ambush. The interrogation scenes are very effective, although this apparent seriousness about getting to the bottom of who is the traitor in UNCLE is spoiled to my mind by the fact that UNCLE's security has allowed a Thrush agent to take a key role in the organisation. Some of these scenes have Prisoner-like overtones - but of course this episode was broadcast the month The Prisoner started across the Atlantic, so perhaps the visual similarity is either in my mind or else something in the popular notion of how interrogation was carried out at the time. The look of glee in the interrogator's face after Solo confesses adds the sado-masochistic dynamic present in some Prisoner episodes. Where UNCLE's security has obviously worked is in nurturing Solo & Kuryakin as such a strong partnership that their partnership takes priority over loyalty to the organisation, ironically leading to the finding of the real culprit. Another way UNCLE isn't shown up in a very good light is that surely the confessions gained by the kind of torture methods shown in this episode should not be taken at face value.
There is of course one whacking great weakness in this episode: it is perfectly obvious who the bad apple is. I mean, seriously, isn't it so obvious that the person looks, acts, dresses, even speaks as the stereotypical baddie of a spy thriller that there can only really be one suspect? - especially if the many references to spy genre are taken into account. It is also obvious that they are mistaken about Struthers are the culprit. The immediate changing of subject in the conference call with UNCLE New York that that is the point. I think it is very clear that this episode functions largely as a vehicle to show off Kuryakin & Solo in the best light, which it certainly does, to the extent of making them look the shining lights of UNCLE!