Shadow of Fear was the 12th produced, and the 19th broadcast, episode of the British television series Captain Scarlet and the Mysterons.
Spectrum is trying to deceive the Mysterons and take pictures of their home planet, Mars. But are the Mysterons too clever for them? Will they be found out and stopped?
At the K14 Observatory in the Greenland Mountains, three astronomers - Dr. Breck, Dr. Carter and Dr. Angelini - are carrying out an experiment. Captain Scarlet and Captain Blue are also on hand, as observers. The astronomers are counting down to begin the picture-transmission from a satellite that is approaching Mars...
They don't yet know, however, that the satellite has exploded - so the countdown proceeds; everything seems to be going according to plan, and everyone's hopeful about seeing the first pictures arrive. But two seconds before that supposed to happen, the countdown stops - and all realize that the satellite's no longer there...
All is not lost, however: it's in fact all part of a plan called “Operation Sword,” conceived by Spectrum. They want the Mysterons to believe they've destroyed the intrusive Earth satellite...so Spectrum can then send the real one without it being detected. At the moment, that satellite is hidden behind a large rock, which is going past Mars. Once it reaches Phobos - one of Mars’ two moons - it will land there and commence taking pictures of Mars itself...
With the first pictures expected to reach K14 the following day, everyone retires for the night - save for Captain Scarlet, who's on night watch, and the too-restless-to-sleep Dr. Breck. He's watching Mars through a telescope - when suddenly the Red Planet starts giving off a huge amount of light, which affects Dr. Breck, until he collapses on the floor - dead! Slowly, two green rings pass over him...and soon afterward, standing beside the scientist's body is his Mysteronized clone!
Once the others find Dr. Breck is missing - and with only a few minutes before the countdown to receive the pictures begins - Captains Scarlet and Blue take up the search, while Drs. Carter and Angelini begin the countdown...
Dr. Breck, meanwhile, is attaching a bomb to one of the gears in the observatory's Gear Rotation Room. Then he heads outside - to face a full-blown Spectrum search party, with Captains Scarlet and Blue getting air-support from Melody Angel and Captain Grey aboard a Spectrum Helicopter!
The chase is on, and Dr. Breck is discovered hiding on top of a cliff-face; he tells the Spectrum agents what he's done and that the bomb will explode the moment the receiver atop the Observatory turns. He and Scarlet exchange gunfire, and Breck is killed...
They try to rush back to the Observatory to warn Drs. Carter and Angelini, but they're too late: the receiver turns, the bomb detonates, the Observatory is destroyed and the two astronomers perish...
Despite the failure of not receiving the pictures, Colonel White states that "Operation Sword" shall continue as planned...
- Aspects of "Operation Sword" resurface in the future UFO episode Close-Up.
- This is the first and only time we see Cloudbase's horizontal jets being used.
- This episode was later used in a compilation video entitled Revenge Of The Mysterons From Mars.
- This episode signifies the last appearances of voice actors Paul Maxwell and Charles Tingwell, who left the Captain Scarlet voice cast due to other commitments. (However, Charles Tingwell’s voice does come back to the series due to the fact clips from previous episodes were used as flashbacks in Traitor and Dangerous Rendezvous.)
- The episode also shows the last vocal appearance of Captain Grey.
- This episode features an error in dubbing - due to the Mysteron voice being different in tone, speed, and reverb; making it seem that Colonel White is imitating The Mysterons. They do share the same actor, though (Donald Gray).
- The events of this story when the observatory was destroyed was seen on a newspaper stand in New York City in the episode The Heart of New York.