Peyton is swinging from the rope "like a vast pendulum. Then, all at once, with terrible suddenness, the light about his shot upward. . ." Peyton interprets this sensation as the rope breaking. He feels himself splashing into the river. In reality, the "noose around his neck was already suffocating him" but in Peyton's mind, he had a chance to escape. He feels himself freeing his hands from the rope, and rushing to the surface of the water. All of this, of course, is Peyton's mind imagining his escape. He is still attached to the rope and is being suffocated.