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." However, unable to sell his unproven idea to France or any other government, Roch begins to lose his sanity, becoming bitter, megalomaniacal and paranoid. The United States Government reacts by tucking him away at a luxurious asylum in New Bern, North Carolina, where he is visited by one "Count d'Artigas"-actually Ker Karraje, a notorious pirate of Malagasy origin. His heterogeneous crew is drawn from "escaped convicts, military and naval deserters, and the scum of Europe." Karraje and his crew lead double lives. Karraje goes around openly, under the alias of "Count d'Artigas", a pleasure loving, slightly eccentric but eminently respectable member of nobility. He is a regular visitor to the ports of the East Coast aboard his schooner Ebba. To outward appearances, Ebba has no other means of propulsion than its sails, but in fact it is pulled by an underwater tug. By this means, Karraje and his crew can pull up to becalmed sailing vessels without raising suspicion and board them without warning. They then rob and massacre the crews, scuttling the ships, adding to the statistics of "unexplained disappearances".