Ante la bandera (Face au drapeau)

In another science-based entry in his Voyages Extraordinaires series, Verne takes us on the journey of Simon Hart, an engineer who poses as a medical attendant to the scientist Thomas Roch. Roch’s invention of a world-conquering weapon has driven him insane. As the paranoid doctor rests in a sanatorium, the vicious pirate Ker Karraje kidnaps both Roch and Hart. Karraje takes them to a secret hideaway in a burned-out island caldera in the Bermudas—but Hart hatches an ingenious escape plan.