Set in 2068, the series depicts a "war of nerves" between Earth and the Mysterons: a race of Martians with the power to create functioning copies of destroyed people or objects and use them to carry out acts of aggression against humanity.
Earth is defended by a military organisation called Spectrum, whose top agent, Captain Scarlet, was killed by the Mysterons and replaced by a reconstruction that subsequently broke free of their control.
Although "Noose of Ice" was originally broadcast after "Flight 104", distributor ITC Entertainment's official running order places it before this episode, disrupting the series continuity.
[5] According to writer Fred McNamara, the episode's "subdued, almost casual tone", which he regards as blending humour with spy themes, "brings a warm, approachable atmosphere to its intimate, neatly unfolding story."
However, he also considers the episode's "languid" flavour to be a downside as well as a strength, arguing that the set-up "really feels as though it should gain more focus" and that most of the aerial tension lies in close-up shots of Scarlet and Blue's "sweat-laden faces".
McNamara also expresses disappointment that the plot point of the secret conference is not developed in later episodes, though he notes that "Noose of Ice" may serve as an indirect continuation.
He concludes that the episode "doesn't rely on death-defying action to constitute effective viewing, but rather digs deeper for that ever-reliable tactic that Captain Scarlet and the Mysterons used so liberally – gently crafting an uneasy atmosphere that builds on speculative horror.