In 1849 Walter Hartright was one of the few survivors of an expedition to British Honduras. Now a letter, pleading for rescue, has arrived from Sir Ambridge Skyllington, the lead explorer. Is it truly he, or is this a fraud? Walter journeys into the jungle to find out, and Theo Camlet goes with him. When they are captured by native partisans Marian Halcombe Camlet sails to the rescue of her husband and her brother-in-law with cases of rifles. But it is 1864, a dangerous time to cross the Atlantic when the Union is fighting the Civil War and the US Navy is on the watch for smugglers.