UFO. The rather unsavoury-looking character depicted is an anonymous van driver (seen in flashback, hence the sepia-tinted monochrome) who tries to rape the female lead, in a key scene which triggers the rest of the storyline. The fairly explicit rape attempt, together with the use of "arty" monochrome sequences and references to drug-taking, all contributed to the episode's notoriety when it was originally shown!
The van-driving sex fiend was played by a bit-part actor named John Garrie (1924-99), who had appeared a few years earlier in another cult show -- Patrick McGoohan's Danger Man. In Koroshi (1968), the penultimate episode of the series, Garrie played the more respectable part of an "Old Japanese Man"... quite a feat for someone who didn't look the least bit Japanese! The role of the mystic sage was right up Garrie's street, however, since he'd been dabbling in the mystic arts ever since the 1940s (he had his first psychic experiences while flying with the RAF during the Second World War).
The "Zen Buddhism" taught by John Garrie Roshi may not have been particularly authentic or traditional, but that doesn't detract from the fact that (judging by the testimonies of his students) he was a first class New Age teacher and guru. But he remained a resolute individualist -- there's a video of him on YouTube where he can be seen preaching Buddhist mindfulness while puffing idly on a cigarette!