My review:
http://www.theavengers.tv/forever/gale1-21vr.htm
As an amateur, I think it has reasonably good astronomy for its time, at least as far as the observatory procedures (theories about the genesis of the Solar System were many and varied in 1963!). Wisely centered around a nice multilevel set, expertly lit (far more convincing than observatories which appear in the color years). A reasonable murder-mystery romp, though with no real clues (to allow the viewer to play, too), and we see very little of romantic Cornwall where it's set (Cornwall is the Southwest tip of England, a storm-lashed former haven of smugglers and pirates, now favored by artists, sailors and walkers). The establishing shot film inserts merely show a London street, not unusual for season 2.
The Avenged?: Two corpses in Cornwall! Veteran telefantasy actor Keith Pyott (Doctor Who, The Prisoner) and also an intelligently-presented ethnic minority role with Dr Rahim. In the first half of the 1960s, The Avengers was actually ahead of most TV series with respect to diversity — odd, when compared with the show's late 1960s stereotyped portrayal of England as white and middle-class. There's also one pseudo-American financier in London: perhaps the first season 2 corpse to avoid blinking at an end-of-Act commercial break!
Diabolical Masterminds?: Grubby profiteers, really, though George A. Cooper has a climactic blazing rooftop gunfight with Macnee (on film), and Philip Latham has a certain sardonic charm as a cardigan-wearing astronomer. A far cry form the evil President Borusa in Doctor Who, yet similar in some ways. Everyone seems to be having a ball, which helps.
The Avengers?: Cathy has an ill-considered furry coat which she seems to share with one of the other characters (Luke Richter)! Steed seems to get only four or five scenes. Cathy's substitution of some slides, which will expose the murderers — in the dark, sneaking about an observatory — is extremely tense, helped by some great suspense music (music throughout is above par for the season). I like her amusement in scenes where Steed tries to learn astronomy (the Boy's Book of... scene and the tag scene). In that Boy's Book of Astronomy scene, where does Steed go? Am I right that he says he is going out, but veers off and vanishes off-set before reaching the front door?
Umbrella, Charm and a Bowler Hat?: Yes, Steed's on form and elegant in his scenes. I can't really imagine him voluntarily sleeping in the bath, though.
Bizarre?: The attempt to shoot from unusual angles results in an unfortunate angle on the backdrop outside the observatory doors. It makes the horizon look so far below us we seem to be on a huge mountain — more Canary Islands than Cornwall. Nevertheless, the set as a whole is superbly detailed and lit.
On Target? (Score): This installment successfully continues with the unusual venues dreamt up for season 2 plots. Not very engaging characters, but mostly well acted. DVD transfer is pretty crisp. Some viewers find the ending hard to follow, so pacing is suspect. There are a few gripping bits though, so I give it a score of two bowlers (out of 4). 5/10.