After two stories establishing the format, this is the first tale that sets up how two people from such disparate walks of life are going to become caught up in each other’s affairs. The first half of the story focuses primarily on Steed as he goes undercover in a counterfeiting ring – those who think that Steed having a boss was a development brought in during the Linda Thorson years may get a surprise to find him working very much in a subordinate role in this story – but when he needs medical help, Keel becomes involved.
Square Root of Evil was the third episode broadcast in the original run, and shows that the producers saw the series still very much in the detective series mould rather than as the spy thriller it would later become. It’s the sort of plot which someone like John Creasey’s pulp hero The Baron, or Leslie Charteris’ Simon Templar (the Saint) would be involved with – in fact, there are strong elements of the 1937 Saint story, Thieves’ Picnic (aka The Saint Bids Diamonds) in the set up.
The original script has some structural issues (notably in the loose ends which are almost tied up by a single line at the end… almost, but not quite), and Big Finish’s decision to make these stories as near as possible to how they were broadcast – rather than, as with the Doctor Who Lost Stories, to rework them where necessary – means they have no option but to follow suit. What would be very interesting (and I’m certain this has crossed their minds already) is for these Lost Episodes to be followed by new episodes featuring Steed and Keel, perhaps picking up on some of these elements left from Richard Harris’ script.
Another strong cast brings the story to life, with unusual roles for Tim Bentinck and Sophie Aldred (even if very occasionally their scenes do bring back memories of Dick Bentley and June Whitfield’s Ron and Eth from Jimmy Edwards’ 1950s radio series Take It From Here). As adaptor John Dorney points out, many episodes of The Avengers end with a big fight, and director Ken Bentley ensures that you can follow what’s happening in amongst the punches.
Verdict: A good presentation of a slightly weaker story. 7/10