Symbolism, Imagery, Allegory
After Bigger kills Mary, the image of her severed head with blood soaking her hair keeps returning to haunt him. As he opens the furnace to see if her body has burned, it appears to him as if the coals are shaped like her body.
The recurring image of Mary’s body and of her severed head reminds him of his guilt, but they also remind him of the fear and shame that led him to kill her accidentally in the first place.