What lurks in the heart of the jungle? High in the Andes, Dane Maddock and Bones Bonebrake discover a secret prison cell where a Spanish explorer lived out his final days. The words carved into the wall seem like the ravings of a madman, but they are the key that opens the door to an ancient mystery. Hidden somewhere in the depths of the Peruvian Amazon is the Inca’s lost City of the Serpent, the gateway to the underworld. Boundless treasure and unimaginable power lie in wait for those who are clever enough to follow the clues left by the mysterious Cloud People. But Maddock and Bones are not the only ones searching for the city, and to get there they must brave the perils of the jungle and the deadly guardians of the underworld as they come face to face with the giant serpent of the Amazon.