The first two episodes ever of The Avengers, which comprise the first half of the box set of four audio lost stories, formed a sort of two part establisher for the series. That make The Square Root of Evil the first stand-alone episode – but it’s still a very different show – even from The Girl on the Trapeze which was to follow in three episodes’ time.
It breaks with the establishing stories in a key respect: where the focus there was on Keel, here it is on Steed. Dr Keel (effectively the show’s star, at this point) doesn’t appear for the first two acts (which seems quite risky so early in the run).
It’s unlike future episodes in another respect: Steed adopts an alternative identity (and an accent!) whereas in most later episodes he’d simply go by “John Steed” (or, in the case of Castle De’ath, as “John McSteed” in deference to the Scottish setting).
Once again we have a very ‘ordinary’ set of criminals – in this case counterfeiters. For some reason 5 (Steed’s boss) is convinced none of them are capable of murder except for ‘The Cardinal’ (I’m spotting a pattern here – after ‘The Deacon’ in The Frighteners – maybe this is what inspired ‘The Bishop’ in Monty Python’s Flying Circus).
There’s also a moll who is beaten while Steed fails to intercede, for fear of blowing his own cover. Along with Steed’s somewhat creepy womanising in this early episodes, it’s another aspect of the shadowy secret service man that is less-than-admirable (an aspect that would later be be submerged by the indomitability and charm).
It’s another superbly produced audio piece (again, the sound design is excellent and the score is energetic and authentic). However, as a story it’s a little more pedestrian, a little less thrilling than the previous episodes.
But from the perspective of continuing to establish the series, introducing Keel late in the play works well; it gives ‘The Avengers’ a chance to face down the villains together, and provides a credible motivation for Keel’s involvement, living up to Steed’s promise in the previous episode to only call on him when necessary. The partnership is now sealed, the premise established, the professional and the talented amateur fighting crime and injustice together.