Having started what turned out to be a monster-long (and still-growing) thread at rec.arts.sf.writen on speculative-fiction television shows, I thought to take a chance on one that seemed well-liked and is available complete on DVD at a reasonable price, that being, of course, the titular Sapphire and Steel. Here are my thoughts on it.
Overall, it's an awfully good piece of work. Its chief merits are two: a gritty and quite dark atmosphere, and pitch-perfect acting from both the two regulars and the supporting casts.
The show was made on a low, low budget, most of which I reckon went on the two stars, David McCallum and Joanna Lumley. Almsot nothing was left for locale or effects, but--in the opinions of many, including me--that ended up an advantage, in that almost all the atmosphere is supplied by hint and innuendo.
The premise of the show must be derived by the viewer from a few cryptic sentences in the opener of every episode. The gist seems to be that our world, or our universe, or our dimension--something like that--is one of a great number that are monitored and warded by some extra-dimensional aliens of power; those alien operatives manifest here as human-looking beings but with powers, and even personalities, tied to some particular "element". Here the show's creators fell down badly, as the "elements" mentioned include both actual elements in the chemical/physical sense, such as copper, lead, gold, and silver, as well as substances such as jet, diamond, and, yes, sapphire and steel. The agent's purposes are somewhat murky, but appear to be involved with repairing potential breaches of reality (and consequent great harms) chiefly arising out of various fiddlings associated with Time. One gets the impression that anything that tends to mix elements from various times can act as a "trigger", allowing malevolent beings of great power access to reality from whatever outside-of-time realm they normally dwell in. Examples of triggers would be doctored photographs that superimpose modern objects on historical backgrounds, or an old house with new rooms added on, and suchlike; those create "weak points" in the fabric of Time. The extra-dimensional wardens dispatch operators to where (and when) such weak points are being actively threatened. The operators, as noted, manifest in apparently human forms, but have extraordinary powers; those powers appear to be unique to each operator, though they have a few in common, such as telepathy. Moreover, as noted, not only their powers but their basic personality types appear to be shaped by what "element" they somehow represent (or, of course, they may have selected an "element" that matches their style and taste).
The show's strong points are several. First, it does not descend to the "as you know, Bob" level of exposition. Exactly what is going on and why and how are more suggested than spelled out, both overall for the program and in particular in each episode, Second, the agents are not classic "good guys': they are aliens, with alien sensibilities, whose chief focus is getting their job done, and they don't have much time or sympathy for the "natives" who may get hurt, or killed, in the process. Of the two stars, Steel is the less human, in keeping with his "steely" nature; Sapphire is more sympathetic and considerate, but this is not a simplistic "good cop/bad cop" shtick, because when push comes to shove Sapphire also is as cold and remote as circumstances require. Even the relations between Steel and Sapphire are, to say the least, peculiar: we are led to believe that they have affection for each other--Steel even mentions the word "love" at one point--yet they can be devilishly harsh with each other (especially Steel to Sapphire).
McCallum is a consummate actor, but though his Steel is excellent, it is, in a way, the role he has played most of his career: the hard, gruff good guy with some really serious chip on his shoulder (Ilya Kuryakin despised the "degenerate" wealthy Western world). Lumley was, at least for me (as I have seen her in almost nothing but the eminently forgettable "New Avengers"), a revelation. She can turn on a dime: her personable smile, used when she wants to be polite to the natives, or friendly with Steel, can go hard and frosty in an instant, and she makes you feel it is a real person reverting to nature, not an actress frowning. She may be the "good cop" of the team, but she too is ever focussed on the crucial mission; she may regret the ugly necessities more than Steel, but she does them just as he does.
Speaking of ugly necessities, another of the "grabber" qualities of the show is that people--sometimes good, innocent people--get hurt or killed, often as a direct consequence of what Sapphire and Steel do. The horrors the operators are up against are not pattycake monsters to be dispatched with a zap: they are immensely powerful beings, who often cannot be "defeated", only temporized with or even placated.
It is also noteworthy that the supporting actors--usually quite few in each episode, another consequence of the budgets, yet another sort of plus--all turn in first-class performances. These things could have come from one or another of the great playhouses of "The Golden Age" of television drama (yes, there really was one).
As noted, budget necessities led to limited locations: an old railway station, an old building, a farmhouse, a single large apartment, and so on, creating a definite "no-escape" sense of claustrophobia that enhances the already dark mood. And the "special effects" are often little more than deep darkness--which, it turns out, is not a bad thing. Too many specfic dramas today (whether tv or film) rely on slathered-on eye candy, to the extent that the visuals rather than the characters and plot become the focus. None of that here, though.
You come away from these (even though they're new enough to be in color) with the feeling that you've just watched some of the better but grimmer black-and-white episodes from the original "Twilight Zone" or "Outer Limits". I would call this one of television's best forays into speculative fiction.