"Treble Cross" is the 24th 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.
Set in 2068, the series depicts a "war of nerves" between Earth and the Mysterons: a hostile 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 murdered by the Mysterons and replaced by a reconstruction that later broke free of their control.
In "Treble Cross", the Mysterons' primary agent on Earth, Captain Black, engineers the death and reconstruction of a test pilot as part of a plot to destroy the world capital, Futura City.
[1] To increase the realism of Major Gravener's resuscitation, the puppet's torso was fitted with a bag into which air was pumped to make it appear that the character's chest is rising and falling.
McNamara's review is not without criticisms: he states that while the crash of the XK-107 presumably destroys the bomber's nuclear warhead, this is unclear from the "fairly compact" explosion seen on screen; he questions the revived Gravener's lack of "crisis of personality" in response to being duplicated by the Mysterons; and he considers the discovery of the reconstructed Harris as the truck driver to be an anticlimax.
[10] Media historian Nicholas J. Cull regards "Treble Cross" as one of several Captain Scarlet episodes that highlight scriptwriter Tony Barwick's interest in the dangers of nuclear technology.