When the body of seventeenth-century mapmaker Johannes Cellarius floats to the surface of a bog in northern Germany with a 57-carat ruby clutched in his fist, the grisly discovery ignites a deadly twenty-first-century 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.

Scrupulously honest Amish-born cartographer John Graf teams up with outlaw prospector and gemologist David Freeman in a ferocious race to find the treasure and break a secret code that will unravel the centuries-old Tavernier stones mystery. But other fortune hunters, opportunists and criminals alike, are in hot pursuit of the mismatched partners—and they'll stop at nothing to possess the legendary jewels.