When the body of seventeenth-century mapmaker Johannes Cellarius floats to the surface of a bog in northern Germany, a 57-carat ruby clutched in his fist, the discovery ignites an international treasure hunt to unearth the fabled Tavernier stones. The hoard reputedly contains some of the world's most notorious missing jewels, including the 280-carat Great Mogul diamond and the 242-carat Great Table diamond. Amish-born cartographer John Graf teams up with outlaw prospector and gemologist David Freeman in a race to break a code that will unravel the centuries-old mystery. But other fortune hunters, opportunists and criminals alike, are also in pursuit, and will stop at nothing to possess the legendary stones.