The Marble Faun is about three American artists in Rome, a city that would be unrecognizable to anyone who has visited in the sprawling metropolis in the 21st century. Until the Industrial Revolution, Rome was underpopulated, described by Hawthorne as a city of mostly ruins, freighted with an intense heritage of music and art but also prone to summer outbreaks of debilitating malaria. The artists--Miriam, Hilda, and Kenyon--are joined by a fourth friend, an Italian Count with a carefree personality named Donatello, who is the uncanny likeness of the Greek sculpture the Faun of Praxiteles:
Donatello's similarity to the titular faun is one of those quasi-mystical touches Hawthorne likes that he never bothers to explain; think of the meteor shaped like the letter "A" in The Scarlet Letter. The Marble Faun borrows heavily from the Anne Radcliffe school of Gothic Romance, including the Roman setting, but refuses to explain away its ghosts Scooby Doo-style, like Radcliffe does. On the other hand, there's is nothing as explicitly supernatural as in Dracula or The Monk--rather, Hawthorne employs these mystical flourishes so matter-of-factly that it seems beside the point to ask for any sort of rational explanation at all.
The other mystical touch in The Marble Faun is a doozy: Miriam gets lost on a group outing to the Roman Catacombs, and when the others find her again, she is in the company of a sinister stranger who may or may not be a thousand-year old phantom haunting the catacombs:
"Inquire not what I am, nor wherefore I abide in the darkness," said he, in a hoarse, harsh voice, as if a great deal of damp were clustering in his throat. "Henceforth, I am nothing but a shadow behind her footsteps. She came to me when I sought her not. She has called me forth, and must abide the consequences of my re-appearance in the world."
[Spoiler alert for the following paragraph.] From then on, the stranger follows Miriam everywhere, stalking constantly at the edge of every room. Miriam, in a strange and ill-advised move, bargains with him that she can convert him to Christianity on penalty of her immortal soul. One night, Donatello, who has fallen deeply in love with Miriam, pushes the stranger over a cliff to his death. The rest--in fact, the bulk--of the novel deals with the consequences of this action, as the guilt from this deed destroys Donatello's once-cheery personality and chases Miriam out of Rome.
Ultimately The Marble Faun becomes a story like The Scarlet Letter, about a single misdeed that becomes a psychological torment to more than the one or two who actually committed it. But where the pyrotechnics of guilt in The Scarlet Letter are enhanced by the repressive Puritan society that proscribes adultery, Miriam and Donatello's guilt seems discordant in spooky, malarial Rome. I didn't find that their anguish--or Hilda's virginal shock--was enough to carry the plot after the intriguing first few chapters. It doesn't help that the novel is padded with material from the journal Hawthorne kept when in Rome, stopping the plot to opine on architecture, painting, sculpture, and other travelogue-type stuff. Though The Marble Faun comes to a satisfyingly creepy ending, set in a masquerade-style carnival, I had already lost interest.