It is 1958 and France's first nuclear submarine, Plongeur, leaves port for the first of its sea trials. On board, gathered together for the first time, one of the navy's most experienced captains and a tiny skeleton crew of sailors, engineers and scientists.
The Plongeur makes her first dive and goes down, and down and down... Out of control, the submarine plummets to a depth where the pressure will crush her hull, killing everyone on board, and beyond.
The pressure builds, the hull protests, the crew prepare for death, the boat reaches the bottom of the sea and finds... nothing.
Her final dive continues, the pressure begins to relent, but the depth gauge is useless. They have gone miles down. Hundreds of miles, thousands...
And so it goes on. And on board the crew succumb to madness, betrayal, religious mania and murder. Has the Plongeur left the limits of our world and gone elsewhere?
***
The Plongeur was a first for France: "an experimental vessel," verily, "powered by a new design of atomic pile, and boasting a number of innovative design features. Its very existence was a national top secret. Accordingly, its melancholy fate went entirely unreported." (p.2) Or it did till today, half a century since its mysterious disappearance. Now, though, its story can be told. And who better than Adam Roberts to do the reporting?
West of the continental shelf, the skeleton crew of the Plongeur—the plunger, if you must—set about stress testing what was then a particularly progressive vessel. In the process, its engineers expect to identify some small problems; instead, the submarine simply sinks.
Something has obviously gone catastrophically wrong, and as the Plongeur is drawn inexorably towards the ocean floor, a collision with which is apt to collapse it—though by that depth the immense water pressure will have long since spirited away the several souls aboard—its crew of courageous countrymen prepare themselves for the inevitable: the end.
But the end did not come. Instead, and gradually, the shaking calmed, and the deep buzz of vibration quietened. It was a very long drawn out diminuendo, the noise and the shaking withdrawing itself incrementally until both had almost disappeared. Impossible to believe that the implacable wrath of the ocean was diminishing—it was against all the laws of physics. (p.28)Unbelievably, this is but the beginning of the Plongeur's story: the end is set in what seems to be a different dimension, and it's years ahead yet.