Despite featuring some interesting on-screen developments in the war with the Mysterons, the wish to avoid the puppets being seen walking indirectly resulted in Spectrum Strikes Back being one of the most convoluted and inconsistent episodes of Captain Scarlet.
The introduction of realistically proportioned puppets in Captain Scarlet had solved several problems but created others in the process. Although the characters were now virtually indistinguishable from real people, any movement they made had to be equally naturalistic. The smaller heads led to the lip-synch mechanism being positioned within the bodies which, now hollow, made the puppets lighter and more difficult to manipulate. In this episode, Tony Barwick's plot finds a solution of sorts by having virtually the whole building move around the characters while they themselves stay virtually static.
Following the events of Operation Time, where it was revealed that Mysterons are impervious to x-rays and susceptible to high-voltage electricity, Spectrum's top brass meet at a lodge in a remote location to unveil some new weapons to fight the Mysterons. In a secret basement room below the lodge, the Mysteron Gun and Detector are revealed but Captain Black is lurking nearby. Black kills Captain Indigo who is reconstructed and then locks the controls, trapping everyone in the basement as the lodge descends to crush them. It is up to Scarlet to pursue Indigo with the new Mysteron Gun and recover the key in time.
It's a welcome change to see development between episodes in one of the Andersons' series, however that sadly peters out further on as the Mysteron Detector is seen only rarely while the Mysteron Gun is not featured again at all - possibly because it's a cumbersome chest-mounted gizmo that would be impossible to run with. It's a shame, particularly as full-size versions appear to have been built for some very brief scenes. It may have been that Spectrum's weapons were later all converted to fire the same stream of electrons, but this is never verified on screen. For all intents and purposes, Spectrum carry on shooting Mysteron agents with bullets and/or blowing them up and it seems to do the job just as well as before. But that isn't the biggest inconsistency as unfortunately the bare bones of the plot do not hold up to scrutiny.
The idea of the whole lodge descending underground for reasons of secrecy is bizarre, as surely any passer-by would become immediately suspicious when a nondescript building started sinking into the ground! Just consider for a moment the extra excavation and hydraulic equipment necessary to create such a building, when a lift or staircase would be much cheaper and quicker to install. Thunderbirds was always keen to depict a fully automated future but this is just taking the biscuit! A descending office-cum-elevator akin to Straker's in UFO would be marginally less preposterous. In a very slow-moving sequence, the lodge descends below ground where the assembled group are deposited, the whole building is then raised up again and a new floor slides in to fill the gap... looking once more like an average hunting lodge. All that just so the characters don't have to walk to the lift, but more importantly to set up the threat later on. It appears even more ludicrous when moments later, Captain Indigo uses the very same lift to take the Detector down to them (heaven knows why the detector isn't down there in the first place). Then once the descent mechanism is set in motion, it can't be switched off from the basement... and the same mechanism has a removeable key and no replacement. Obviously Spectrum don't have a Health and Safety department! Good job they installed that skylight for Scarlet to jump through later on. In short, the plot - if it can be called that - has more than a few holes and doesn't benefit from any sort of analysis.
In a link with the opening episode, the World President makes another appearance - though he appears to be still wearing the same suit. His subsequent non-appearance may have been down to Paul Maxwell's departure, as he and Charles Tingwell were not available for the later recording sessions. The earlier episodes are also characterised by the regular appearances of a smaller number of guest puppets, with the MEV Navigator from The Mysterons and Richards from Manhunt cropping up here in different roles. Leo Tolstoy once referred to music as 'the shorthand of emotion' which is an apt description for the role of Barry Gray's soundtrack in a puppet series. So, despite the limited range of heads each character had, the music punctuates and supports the action as well as ever.
The episode provides a bit of a breather for the effects crew as there are much fewer vehicles on show, with just a few saloon cars involved in the chase and some filler material with the Angels at the opening (the lodge would later reappear unchanged in Special Assignment). This results in it being a more talky episode than usual. As for the dialogue, much has been made of the series' perceived lack of humour but this is not entirely accurate, at least when considering the early episodes. There is some light relief in the earlier scenes of Scarlet and Blue relaxing and the use of the Mysteron Detector to 'shoot' the duck which is on the menu later. However, when the Mysteron threat refers to 'the mystery of the Mysterons', one gets the feeling that the script would have benefitted from at least another draft.
Captain Scarlet featured many improvements on the Andersons' earlier series, with more elaborate effects sequences, increased attention to lighting and an equally stirring soundtrack. The use of realistically proportioned puppets still divides opinion even now, yet the series' obvious shortcoming when compared to its predecessors is the occasionally poor plotting and inconsistent approach to internal continuity which in the case of Spectrum Strikes Back lets the episode down.