When a mysterious envelope arrives for Jake Ransom, he and his older sister, Kady, are plunged into a gripping chain of events. An artifact found by their parents—on the expedition from which they never returned—leads Jake and Kady to a strange world inhabited by a peculiar mix of long-lost civilizations, a world that may hold the key to their parents' disappearance. But even as they enter the gate to this extraordinary place, savage grackyls soar across the sky, diving to attack. Jake's new friends, the pretty Mayan girl Marika and the Roman Pindor, say the grackyls were created by an evil alchemist—the Skull King. And as Jake struggles to find a way home, it becomes obvious that what the Skull King wants most is Jake and Kady—dead or alive.

Using his father's watch as a key, Jake intends to return to Calypsos. Instead he's thrust into a strange desert land where he's joined by his friends Marika, Pindor, and Bach'uuk and his sister, Kady. As they try to figure out what to do next, a surprise attack by the beautiful young Princess Nefertiti takes them all captive. Soon even she is battling the Skull King's minions. For Jake has something the Skull King wants—a prize that will give its owner awesome power, including control of the fearsome Howling Sphinx. In a new pounding adventure, Jake races against time to outfight and outwit Kalverum Rex, knowing that if the Skull King wins, he'll be unstoppable. Filled with unexpected danger, challenging puzzles, and dazzling action, this is a first-rate, fast-paced thriller—a read only James Rollins could have created!