Like The Begum's Millions, which Verne published in 1879, it has the theme of France and the entire world threatened by a super-weapon with the threat finally overcome through the force of French patriotism.

Thomas Roch, a brilliant French inventor, has designed the Fulgurator, a weapon so powerful that "the state which acquired it would become absolute master of earth and ocean."

The United States Government 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.

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.

Following publication of the book, Verne was sued by the chemist Eugène Turpin, inventor of the explosive Melinite, who recognized himself in the character of Roch and was not amused.

The character of Roch and his revolutionary powerful explosive might also have been inspired by the real-life Alfred Nobel who invented dynamite and later reportedly regretted having introduced such a destructive force into the world.

[2] Film historian Thomas C. Renzi considers Roch the archetype of the "mad scientist," the thriller fiction stock character of a monomaniac whose warped genius endangers the world.