OK, finally an episode caught my interest: The Russian spy plot, and the sub-plot about the cute detective, Sam, and the investigating reporter, Ruth, who wants a scoop so she can leave their small hamlet, move to the big city, and work for The Times! I loved Sister Boniface's little daydream envisioning Sam as Captain Von Trapp and Ruth as novitiate Maria. Also enjoyed everything about the cigarettes [which, of course, everyone around is smoking - I REALLY don't miss THAT!], and Sister Boniface's scientific testing thereon. I also enjoyed the sister's reference to her Lord Peter Wimsey collection. Now, THERE was a great detective - created by the wonderful Dorothy Sayers. It's a shame there aren't more TV writers out there of that ilk, or at least aspiring to be of that ilk.
But I have to agree with those who complain the sister talks too fast, especially when she's conveying important scientific information. And I would rate the ep higher, except for the PC/w0ke anachronisms which take one out of the story, e.g., calling an "actress" an "actor," and the ever-present casting of an unrealistically ethnically diverse English village of the '60s. But the BBC has its guidelines, and no exceptions are made, even for period pieces. So annoying. So dumb. So insulting to their viewers.