Thomas Roch, a brilliant French inventor, has designed (but not yet built) the Fulgurator, a weapon so powerful that "the state which acquired it would become absolute master of earth and ocean." The weapon is so powerful that (as we see later in the book) a shell shot from the Fulgurator need not hit the target at all— the vibrations in the air when the shell passes over a ship are enough to break the ship into pieces. However, when Roch attempts to sell his design, no one believes his weapon can really work. He first tries to sell it to the French government, asking for a lot of money, and is turned down. He then tries Britain and United States. Unable to sell his unproven idea, Roch becomes bitter, megalomaniacal, and paranoid. The United States Government finally reacts by tucking him away at a luxurious asylum in
New Bern, North Carolina, where he is visited by Ker Karraje, a notorious
pirate of
Malagasy origin. Karraje and his men kidnap Roch and his attendant Gaydon from the asylum and bring him to their hide-out, the island of Back Cup in
Bermuda. Here a wide cavern, accessible only by submerged submarine, has been made into a well-equipped pirate base. It is revealed that Gaydon is actually Simon Hart, a French engineer and explosives expert sent to spy on Roch and gain his confidence. Roch begins constructing his fearsome weapon, happily unaware that he is nothing but a glorified prisoner in the pirate's hands. Hart succeeds in secretly sending out a message in a metal keg, giving the full details of Karraje's operations and his impending acquisition of the Fulgurator. The message gets through to the British authorities at their nearby naval base in Bermuda, and they send a submarine, , to find Hart. The submarine's crew makes contact with Hart, and take him and Roch on board, but the
Sword is discovered, attacked, and sunk by the pirates. The unconscious Hart and Roch are extracted from the sunken British sub by pirate divers, leaving the entire British crew to perish. Hart manages to avoid suspicions of his actions. Meanwhile, Roch's weapon is completed and becomes operational. Roch has no compunction in using it on British or American ships, and easily destroys the first cruiser to approach the island, with only a handful of its crew surviving. Next, a ship arrives from France, but Roch refuses to fire on his own country's ship. He struggles with the pirates, who try to seize the Fulgurator. During the struggle, Roch blows up himself, his weapon, and the pirates, along with the entire island. The single survivor of the cataclysm is Simon Hart, whose unconscious body with the diary at his side is found by the landing French sailors. Hart is eventually revived, to be amply rewarded for his dedication to his country. ==Response==