For the past two years, scientific buoys, immersed at a depth of two thousand meters in the Mediterranean off the French Riviera, have attracted countless species of pelagic fish, among them the Giant Oarfish also known as the King of Herrings, drifting vertically, alone or by pairs. With the help of the world expert in Giant Oarfish and the logistic collaboration of enthusiasts, a scientific expedition reveals the biology of this enigmatic ambassador of the abyss. Thanks to underwater robots, mixed-gas dives, and revolutionary images (5k, high speed, UV, and X-rays), the film shows for the very first time when and how the creature feeds and reproduces. We thus raise the veil on its paradoxical habits: why do all the adults self-mutilate and rid themselves of two-thirds of their bodies without being affected? Why does this lethargic fish not have any known predators? Why does it sometimes strand, while still alive, on shores often in pairs? Why is this ghost of the abyss attracted by electric cables?