One of the gamblers infesting the Mississippi boats gets a punch-up from the pards and begins to squeal: thats how the pards discover that New Orleans is hell in thrall by an underworld ring of racketeers headed by the mysterious Maschera di Ferro [Iron Mask]and his Sudanese lackey Hanubi, who is in league with the Cuban clan. The ruffians linked to the black followers of voodoo are blackmailing the wealthiest people in town with threats and kidnappings, and at the slightest slip-up they have absolutely no hesitation in suppressing their own affiliates, resorting to snakes and poison-tip arrows! In this anxiety-ridden atmosphere sheriff Nat Mac Kennet has no option but to give Tex carte blanche.