In American TV series there is a tradition that each season has precisely one episode (sometimes referred to as a clip show episode) that consists almost completely of clips from earlier episodes. Typically this is done by making two or more protagonists reminisce about their exploits. As a 1960s British TV series, The Avengers thankfully does not follow this tradition. However, after a change of production teams one of the earliest Tara King episodes produced was reworked by the new team into something that has pretty much the same feel, even though there is only a small number of scenes taken from earlier episodes and most of the clips are original. (To the original episode that is, which unfortunately we can't watch instead.)
This episode is a bit of a counterexample to the principle that the quality of an experience is determined by the beginning, the end, its best moment, and its worst moment:
The beginning, a spoof of
Arsenic and Old Lace (1944), is extremely strong. The end, in which Steed is irritated by the fact that Mother's assistant never speaks, and tries to do something about it, is slightly better than the average Steed/King ending. The problem is that the beginning is also the high point, and is followed immediately by the low point: the set-up of the boring framework in which Mother tells the original story.
Despite these problems, I did enjoy this episode because there is enough of the original version left to be genuinely interesting. It's framed to make it ridiculous, but personally I don't mind. Ever since the days of Tara King's predecessor Mrs. Peel, the series has never taken itself very seriously anyway. I assume I would have enjoyed the original version even more, but apparently it is lost. (To be honest, the material that didn't make it into the clip show may have been awful; it seems unlikely, but we just don't know.)
The story told in the clip show concerns Intercrime, and is a continuation of
Intercrime (1963), an episode of the era before the series was sold to the US, featuring Mrs. Peel's predecessor Mrs. Gale.