"Avalanche" is the 11th episode of Captain Scarlet and the Mysterons, a British Supermarionation television series created by Gerry and Sylvia Anderson and produced by their company Century 21 Productions. It marked the scriptwriting debut of Century 21 voice actor Shane Rimmer, and was first broadcast on 27 October 1967 on ATV Midlands.
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. Scarlet's double has a self-healing power that enables him to recover from injuries that would be fatal to anyone else, making him Spectrum's best asset in its fight against the Mysterons.
In "Avalanche", the Mysterons destroy and reconstruct a maintenance technician and his snowcat to attack the Frost Line Outer Space Defence System in Canada.
Plot
The Frost Line Outer Space Defence System is a network of missile bases in Northern Canada, tasked with protecting Earth from extraterrestrial threats. In a transmission to Earth, the Mysterons (voiced by Donald Gray) warn Spectrum that they intend to attack key Frost Line installations. They use their powers to destroy a snowcat driven by maintenance technician Eddie and reconstruct both Eddie and the snowcat as agents in their service. The reconstructed Eddie passes security at two bases – Red Deer and Cariboo – and plants devices inside their ventilation systems that render the air unbreathable, killing 250 personnel at Red Deer and 70 at Cariboo.
In a transmission to Cloudbase, the belligerent Frost Line commander General Ward warns Colonel White (voiced by Donald Gray) that he will fire missiles at Mars if another base is attacked. Fearing the Mysterons' response to such an action, White orders Captain Scarlet and Lieutenant Green (voiced by Francis Matthews and Cy Grant) to investigate Red Deer. Arriving at the base, the officers discover that the personnel have suffocated not due to the introduction of a toxic gas, but the removal of all oxygen from the air.
Obtaining a Spectrum Pursuit Vehicle from a trapper, Scarlet and Green speed to the next base, Big Bear, only to learn that Eddie has already passed through and is now on his way to the Frost Line command centre. After knocking out a guard who is barring entry to the base, Green removes Eddie's oxygen-depletion device from the ventilation system before it can affect the air. Meanwhile, Scarlet takes the SPV and chases Eddie. The snowcat is carrying liquid oxygen, which Eddie dumps into Scarlet's path to force him off the road. Scarlet draws his gun and fires several rounds into a snow-covered slope nearby; this triggers an avalanche that pushes the snowcat over a cliff, causing it to explode on the rocks below. With the command centre saved, Ward, no less arrogant than before, radios Cloudbase to make peace with White.
Production
Actor Shane Rimmer had a prior association with Century 21, having voiced the character Scott Tracy in Thunderbirds and narrated the series' alternative two-part episode format. Impressed by his work, the Andersons asked him to write an episode of Captain Scarlet. Rimmer immediately agreed and was soon telephoned by series script editor Tony Barwick, who had an outline for an episode titled "Avalanche" and told Rimmer that a courier would "'[drop] the storyline over to you in about an hour. Take today and tomorrow and see how you'd go about filling it in.'" Resigning from his part-time job at a sheet metal factory to focus on this task, Rimmer put together a draft treatment over the next 24 hours; he found the characters and plot elements a "heavy mix to juggle with" but managed to incorporate "one or two workable story developments that avoided stepping on the toes of the series concept or any of the main characters." Rimmer and Barwick revised the draft two days after. After the script for "Avalanche" was completed, Rimmer started work on treatments for the episodes "Expo 2068" and "Inferno" – jobs that, in his words, "more or less took care of '67". He later wrote scripts for Joe 90, The Secret Service and The Protectors.