In 1820 a notorious Spanish pirate was caught in a fierce battle along the California coastline, narrowly escaping into the foothills with a priceless treasure. Now, almost 200 years later, the legendary pirate’s skeletal remains are discovered in the quiet coastal town of Knightsbridge, California, along with a tantalizing clue to the treasure’s whereabouts. As news of the discovery spreads, the town is swamped with thousands of amateur treasure seekers as well as Treasure Finders Incorporated, a powerful organization with an impressive track record of discoveries. When classmates Will, Mikey, Susan, and Evelyn learn of the discovery, they are unable to resist the urge to join in the hunt. With Will's knowledge of the outdoors, Mikey's electronics expertise, Susan's computer wizardry, and Evelyn's photography skills, they are certain they can unravel the pirate's secret. Facing long odds, the seventh-graders embark on an adventure of a lifetime, discovering that the mystery deepens as they desperately hunt for clues, decipher historical landmarks, and match wits with their ruthless competitors.