State Road 177 runs along the Suwannee River, between Fargo, Georgia, and the Okefenokee Swamp. Drive that route from east to west, and you’ll cross six bridges. Take it from west to east, and you might find seven.

But you’d better hope not.

Titus and Melanie Bell leave their hotel in Fargo for a second honeymoon canoeing the Okefenokee Swamp. But shortly before they reach their destination, they draw up to a halt at the edge of a rickety bridge with old stone pilings, with room for only one car . . .

When, much later, a tow-truck arrives, the driver finds Titus lying in the middle of the road, but Melanie is nowhere to be found.