On a July night in 1987, a cartographer named Elise Thibodeaux arrived at a dead-end road outside Terrebonne Parish, Louisiana, to map a stretch of Bayou Corbeau that didn't appear on any government survey. She carried a compass that spun in circles, a stack of blank paper, and a lantern that went out every time she tried to sketch the water. I met her at dawn on the gallery of her rented shotgun shack, her hands stained with ink that smelled like rot. She showed me the map she'd drawn—every cypress knee in position, every bend of the channel exact—except for the center, where the paper was eaten through, a ragged hole the size of a dinner plate, the edges wet and grey. She said the bayou had drawn itself onto her paper while she slept, and that what filled the missing section was not meant to be seen by human eyes. She whispered that she had seen it anyway, in a dream, and that now the bayou knew her name.