"We weren't going to play murders until after dinner."
IN THIS ONE... The youngest in the cast are killed. Sapphire and Steel discover McDee was working on a universal vaccine, but fated to let a plague loose on the world.
REVIEW: The truth (or at least ONE truth) is out. Old McDee was developing a super-vaccine and would soon have a little accident, releasing lethal bacteria (the science is something musty; don't look at it too closely) that would eventually doom mankind. Except that never happened because McDee died before it could. And he must die again. Is the Enemy trying to change history? Can Sapphire and Steel put it back on track? It seems they can interact with a manifestation of McDee (once again, Sapphire shows powers akin to the Enemy's, though only reluctantly), but is this the same entity as the one presumably puttering away in his lab? The episode answers some questions, but asks many more, which is what this show is best at.
Of course some of those questions seem to be red herrings. The whole whodunit murder mystery element, for example. Veronica is killed, but her body disappears. Her boyfriend Tony, the likely suspect according to Sapphire's psychic reading (he was having an affair with Mullrine's secretary), is shot just before dinner. Is this just a murdery bunch (Tony will only trust Steel, a stranger), or does the temporal breach figure in? Is it significant, for example, that the two youngest party guests are the first to be killed? Will it go up the line like that leaving only the people who were alive in 1930? Knowing what we know of McDee himself, this does feel all rather irrelevant, like something happening in the background to distract our heroes from the real threat. Or perhaps the Enemy is creating the narrative for some other purpose. Steel talks about these circumstances like one would a story, as if it weren't real. And old Mrs. McDee thinks it's all rather like Agatha Christie's Ten Little [insert racist word here], hammering at the idea a little too obviously. The script does subvert the tropes though. There's a drawing room explanation, but it's not about the murders. As disturbing as vanishing bodies is vanishing memories which can't be explained (unless you're Steel forgetting your cover name, which only merits an eye roll from his partner).
A few words on the direction, which I've neglected until now, but really should commend. In addition to juggling a large cast in a closed space, Shaun O'Riordan always finds the time to craft some interesting shots. Part 2 had Sapphire and Steel lit by the hellish flames of the anniversary cake. Part 3 heightens the paranoia of a scene by tracking back from one room to another, as the time elements look on the assembled group of suspects. Sapphire reading "Murder Me Twice" is a prescient bit of foreshadowing. The simple effects work rather well, whether it's Tony terrified in the blue light of whatever is behind all this, or the breakaway chair. He's doing a fine job with the program's least atmospheric script to date.
ON THE OTHER SIDE OF THE VORTEX: The Doctor actually met Agatha Christie once, in The Wasp and the Unicorn.
REWATCHABILITY: Medium - It's the tipping point where we (think we) know what's really going on, but those whodunit distractions could become an annoyance.