I vaguely remember The Man from Uncle TV series repeats as a kid but only got reacquainted with the show when the spliced together movies were regularly shown in the 1980s when its campy nature was more apparent.
In this film, no spy seems to be missing unless you count Kuryakin wandering around the Soho area of London looking for pussy. I mean the four legged kind even though the producers would had been well aware that Soho was a notorious red light district!
The plot involves reversing the ageing process and cats have been used for the experiments hence why Kuryakin is looking for missing cats in a studio bound London setting.
Napoleon Solo gets to chase ladies as well as making sure THRUSH does not get the youth rejuvenating formula with a plot of a senior diplomat being at risk of being kidnapped, de-aged and put under the control of THRUSH.
It is all very silly, all shot in California with the tunes of Rule Brittania every time the setting moves to England.
Bernard Fox is the standout as the THRUSH villain Jordin who brings the right balance of menace and humour.