This one's easily the best "Beasts" episode: the plot involving lycanthropy, and putting forth yet another of Nigel Kneale's controversial theories of evolution is most intriguing; the whole, then, is transfixed by an unforgettable performance from a typically intense Patrick Magee.
He plays an eccentric and reclusive old scientist (with long scruffy hair and a high-handed attitude to match) who believes that humans evolved from wolves and has been attempting to restore the link in his private laboratory (situated above a pet shop owned by his long-suffering middle-aged daughter, whom he actively resents). His activities arouse the suspicions of a dogged young R.S.P.C.A. man the latter's initial worries simply concern the safety of the wolves, but he soon realizes that he's bitten off more than he can chew. Magee himself doesn't shy away from expounding on his particular line of work deliriously 'corroborating' his arguments by frequent references to the Little Red Riding Hood folk-tale (from where the title of the episode itself emanates, incidentally) and in which he states that Grandma wasn't gobbled up as we'd been led to believe but rather she was a werewolf to begin with!
Eventually, Magee succumbs to "acute blood poisoning" (naturally, he was his own guinea pig) during a critical point in his experiments his last act, compounded by howls in reply to the caged animal's own calls, takes the form of an impromptu speech to an imaginary gathering of fellow (and previously disapproving) colleagues; incidentally, the man from the R.S.P.C.A. is forced to "put down" the wolf, having been injected with the serum as well. The woman's liberating reaction to her father's death results in the decimation of both the shop and the lab in fact, everything that reminds her of Magee; about to vent her anger on the scientist's shrouded corpse itself, we then get a subliminal facial metamorphosis