Dick Ralston is dead by his own hand. Playboy, scion, heir to a vast mining fortune: Dick Ralston had everything to live for. His varsity charm and ruddy good looks betrayed not the least indication of inner disorder. Yet he put a bullet in his head just the same, as did three other men like him. The police, baffled, surmise the workings of a secret society, a thrill-kill suicide cult. But Alan Caranac, Ralston's best friend, suspects foul play of a darker kind. Caranac is a flaneur, an ethnologist, a scholar of the occult with a nose for the supernatural. And Dick Ralston's death stinks in his nostrils.

When Caranac learns of recent withdrawals from Ralston's bank account, his investigation leads him to Renè de Keradel, an imperious psychiatrist, and his beautiful daughter, the Demoiselle Dahut. de Keradel believes he's on the verge of a scientific breakthrough. Memory, he claims, is heritable and thus recoverable. Ten thousand years of forgotten lore, the accumulated wisdom of mankind going back to the invention of agriculture: a universal library more vast than a hundred Alexandrias, engraved not on scrolls or papyri but recorded in the brain itself. Whoever decodes these mnemic traces stands to inherit not gold or gemstones but something incomparably more valuable: total knowledge and the power of its exploitation, enough to elevate its possessor to godhood—even to eternal life.

But what has this project to do with de Keradel's bloodline, which stretches back into prehistory, into ancient Armorica? What is Dahut's connection to the legendary city of Ys, drowned beneath the ocean in consequence of its sin and wickedness? And why does Alan Caranac know more about these things than he can account for?

Before long Caranac is embroiled in a conspiracy of human sacrifice and demonic power, beset on all sides by blackest sorcery, but bound also by the sinews of a love that transcends space and time. Can he thwart a dark power, long dormant, that would again make subjects of men's souls? Or will he, too, become a victim of Dahut's ombromancy, dead in the meat of his body but alive forever in its severed shadow? Continuing from events in Burn, Witch, Burn, but requiring no knowledge of that book, Creep, Shadow! is A. Merritt's supreme fantasy.