Two friends are midway on a canoe trip down the Danube River

Throughout the story Blackwood personifies the surrounding environment—river, sun, wind—and imbues them with a powerful and ultimately threatening character.

Most ominous are the masses of dense, desultory, menacing willows, which "moved of their own will as though alive, and they touched, by some incalculable method, my own keen sense of the horrible."