Rocket-ships, explosions, clanking machinery – these were the unforgettable sounds of Supermarionation series like Thunderbirds, Stingray, Captain Scarlet, Supercar, Joe 90, Fireball XL5 and more... but where did they come from? In this behind the scenes documentary, we delve into the archives to uncover the secrets behind the sounds – along the way uncovering lost dialogue recordings and isolated effects unheard for over fifty years. Forgotten reel to reel audio tapes from AP Films in the 1960s represent a treasure-trove of newly rediscovered Gerry and Sylvia Anderson rarities. Some technical experimentation was required to reveal their contents – a process that involved careful playback of 60 year old quarter inch tapes on antique equipment. Along with archive interviews from director David Elliot and sound effects wizards John and Jean Taylor, the story of how unforgettable soundscapes were created for some of television's most beloved action-adventure series.