In December 2006 on a quiet, picturesque section of the Sapelo River just north of Eulonia, Georgia, a young man doing some routine landscaping made a seemingly harmless discovery. An old cast iron container had poked its way out of the eroding riverbank and tumbled within a few feet of the water’s edge.

The structure, withered away by time, at first appeared to be a discarded fuel tank, far from a novelty item. But a closer look at the capsule, found on the shores of Fairhope, a plantation property roughly 50 miles south of Savannah, revealed something much more cryptic. Literally.