The abyss for Hester Prynne was faced and held at bay when she faced the community and was punished for her sin. Her confession reduced the power of the abyss to harm her, though she lives each day now watching over her child, fearful that the abyss might claim Pearl as it once tried to claim her. Dimmesdale is the character who is faced with the abyss most clearly and who fails because he cannot look into it and challenge its dangers. He has not confessed his sin, and so the abyss casts a pall over him that eats away at his mind and body until it finally kills him. Chillingworth has fallen into that abyss. The spiritual danger represented by the abyss has claimed Chillingworth and has turned him into an avenging spirit, an emissary from the abyss, as it were, who torments Dimmesdale every day until the preacher is destroyed.
The idea expressed by Melville is that we face dangers every day, and for Melville it is likely that he means spiritual dangers, attempts to entice us into sins and errors that will destroy us. Many characters fail to escape the abyss, though some--like Ahab--may be dragged into it in a heroic attempt to fight back. Other characters, such as Dimmesdale, are drawn in slowly and lack the will to escape. Ishmael escapes, as does Hester. They achieve a spiritual knowledge of themselves and the world that leaves them on the edge, facing new dangers, but not p