Jebediah Coffin, the youngest of the captain's sons, asks his closest friend, a young Boston physician, to treat the old man. Dr. Davis Bentwood considers himself a modern man of science. He has rejected superstition and religion in favor of the latest rage, the Transcendental teachings of Ralph Waldo Emerson, poet and philosopher. But nothing in science or philosophy can explain what is happening to the Coffin family.

The evening of Bentwood's arrival, the captain's infant grandson is found frozen, rock solid, in a crib only yards from a roaring fire. Another son, an experienced ship's master, perishes at sea under disturbing circumstances that defy a natural explanation. The Coffin family home is pervaded by an atmosphere of impending doom that grips everyone with dread, even the usually indefatigable abolitionist Frederick Douglas and the outspoken suffragist Elizabeth Cady Stanton. Even the warm feelings growing between Bentwood and Jeb's lovely cousin Lucy are affected by the malign spirit that seems to hang over the mansion.

Bentwood seeks the dark heart of a mystery that seems inexorably linked not just to the Coffin family but to the very fabric of the American nation. The novel's powerful climax vividly recalls "The Fall of the Houser of Usher," as Bentwood struggles to save not just his life but his very soul.