A very good episode with, for Hammer, an unusual sociological theme revolving around an original (and fascinating) premise, where a system of 'prison without bars' is tried on an inveterate petty thief (played by a young Brian Cox). The identity of his deceptively sympathetic captor (the ever-reliable Hammer stalwart Peter Cushing in his final effort for the studio which made him famous) supplies a twist eventually which is, frankly, predictable
but, imbued with the star's idiosyncratic pragmatism and authority, the characterization is completely believable chilling in its implications, but still essentially human. The pet-shop-housing-a-private-zoo setting adds flavor and excitement to the already tense proceedings (aided immeasurably by having two such powerful, yet totally opposite, personalities at work); along the way, Cox' wife and even a police sergeant become involved in the situation. Improbable though it may be, the final twist in which Cox and wife discover they've merely exchanged one prison for another, with rescue a lot harder to come by this time around! is a real beauty; this is actually followed by yet another involving Cushing's own ironic fate. By the way, the title refers to the sound-proof, electrically-wired booth in which virtually all the characters end up at one time or another. Director Gibson had helmed the last two sorry entries in the Hammer Dracula series; he proves more adept at dealing with psychological - as opposed to supernatural - issues.