"Inferno!" is the twenty-ninth instalment of Captain Scarlet and the Mysterons. Written by Tony Barwick and Shane Rimmer and directed by Alan Perry, it was first transmitted on 16 April 1968 on ATV Midlands.
In this episode, the Mysterons destroy and reconstruct a spacecraft to attack a desalination facility in the Andes mountains.
While tracking down space debris, the Euro-Space recovery vehicle SKR4 is destroyed by a meteoroid impact. Informing ground control that the crew are abandoning their mission due to a technical fault, a Mysteron reconstruction of SKR4 reverses course for Earth.
On Cloudbase, Spectrum learns the target of the Mysterons's latest threat: the Najama complex, an automated facility in the Andes that desalinates seawater to irrigate the interior of South America. Colonel White dispatches a team of field agents, led by Captain Scarlet and Captain Blue and accompanied by the Angel Flight, to the Najama Valley to set up surveillance posts around the complex. Shortly after Spectrum's arrival, Captain Black slips into the ancient Aztec temple where Captain Scarlet and Captain Blue are based and conceals a radio transmitter in the mouth of a statue of the Sun God.
Meanwhile, Euro Tracker station is monitoring SKR4's return journey to Earth. When attempts to contact the spacecraft fail, a concerned Major Moran alerts Cloudbase. But transmissions between Euro Tracker and SKR4, as it proves, are being jammed by an external radio signal that is drawing the spacecraft off-course to a new landing site in the Najama area. Colonel White deduces that SKR4, which is carrying several explosives packs, is being used as a missile to strike the Najama Valley.
As SKR4 enters Earth's atmosphere, Captain Scarlet and Captain Blue discover that the source of the signal--the transmitter which Captain Black has hidden--is located somewhere within the temple. Realising that there is not enough time to find and destroy the transmitter, they evacuate the temple in their Spectrum Pursuit Vehicle, and Captain Scarlet orders the Angels to launch an aerial assault on the building. Although the statue of the Sun God is destroyed in the ensuing bombardment, the Spectrum personnel are too late to prevent SKR4 from crashing into the ruins. The impact triggers a landslide that hits the Najama complex's exposed liquid oxygen tanks and destroys the facility in a series of explosions. "It's an INFERNO!!!" Captain Blue blurts in horror. Captain Scarlet concedes that the Mysterons have won that round. "But the fight--isn't over yet!" he adds.
"Inferno" was filmed in late 1967. Most of the episode's incidental music consists of cues recycled from older Supermarionation productions: seven earlier episodes of Captain Scarlet as well as six episodes of Thunderbirds and three of Supercar. The puppet playing the SKR4 navigator does not appear in any other episodes of Captain Scarlet.
"Inferno" features the third appearance of the Mysterons' vanishing power that was previously seen in "The Heart of New York" and "Model Spy".
The SKR4 Pilot is the uncredited voice of Shane Rimmer, mostly known for playing Scott Tracy in Thunderbirds.
"Inferno" is considered to be the best episode of Captain Scarlet by TV Zone magazine, which praises the episode's "dark direction and straightforwardly effective plot". "Little touches" – such as the realism of Black's cautious ascent of the Sun God statue, and Scarlet and Blue being on first-name terms (making them "real people, with real names and lives behind their codenames") – are also positively received. What is most to the episode's credit, comments the magazine, is its downbeat ending, aggravated by the fact that "Spectrum's efforts actually make it worse".
James Stansfield of the website Den of Geek ranks "Inferno" sixth in his "Top 10" list of Captain Scarlet episodes, praising its "horror movie-style elements" and comparing Scarlet and Blue's "[creeping] about the temple looking for clues" to an episode of Scooby-Doo. Describing the episode overall as "tremendously fun", he also commends its point of view shots and "echoey footstep" sound effects as well as its depiction of the "comradeship" between Scarlet and Blue. He argues that as with other episodes in which the Mysterons' plans succeed, Spectrum's defeat adds to the excitement by creating an "'anything can happen'-type feeling".
Commentators Chris Drake and Graeme Bassett suggest that SKR4 being under the control of an agency called Euro-Space shows that the episode's writers were "keen to establish the existence of a European space operation in addition to the obvious American space programme".
- In 1993, the instalment was also a small paperback in a series of eight books, written by Graham Brown, illustrated by famous artist Richard Chasemore and published by Boxtree.