After the sinking of the Rio Toro, the sole survivor is murdered by a beachcomber for his money and the valuables he carries. Then Pedro Montero travels to remote Venezuela, where he sets up a store to serve the balata expeditions. The Comte de Monte Bello, on a expedition of his own comes across this rude and ruthless owner; eventually finding his hoard after he defends himself from the storeowner. The bonds which Montero had hoarded, and the Comte retrieves, are cashed and the bank wants to know where they came from, since they were listed as ?lost at sea? and replaced. Nelson Lee and Nipper are hired to unfold this mystery?and this all leads them to the Black Wolf!