There are many ways in which The Scarlet Letter and Moby-Dick contain Dark Romanticism and accompanying preternatural events. Remember, Dark Romantics are interested in sin, self-destruction, and alienation. All of these are found in The Scarlet Letter. We have the sin of Hester's adultery, which is also Dimmesdale's sin.

It might be a bit harsh to say that adultery was an act of self-destruction for Hester. It seems more accurate to say that it’s Puritan society that tries and fails to destroy Hester’s sense of self. However, the adultery does take a toll on Dimmesdale's psyche, which could be another form of self-destruction.

Finally, we have alienation. Hester, Pearl, and Dimmesdale all experience some sort of alienation, even if Dimmesdale's is more psychological. Sin, guilt, and alienation lead to some preternatural occurrences, including Pearl's relationship with the forest and the meteor that makes the letter "a" in the sky.

Of course, sin, self-destruction, and alienation course through Moby-Dick as well. We have the sin of hubris in Captain Ahab. He thinks he can actually kill the whale. Ahab's single-minded determination leads to his literal self-destruction. He dies in the end. More so, his drive to kill the whale alienates him from society, since it puts him out at sea.

As with The Scarlet Letter, the sin, self-destruction, and alienation leads to some preternatural occurrences and company. Ahab himself, with his missing leg, is rather unusual and almost ghoulish. Fedallah, too, is preternatural, with his supposed prophetic talents. Then there's the "whirlpool," which might seem like something out of a science fiction movie.