From the book jacket:
The mansion stands on the rue de Courcelles in the heart of fashionable Paris, a grim fortress of a building with gates tightly barred and windows shuttered. It is a fit setting for those who inhabit it, the decadent, aristocratic members of a dying family who share a deadly secret, and who must keep that secret, or perish.
Most in danger is the one child in the house, son of Colonel de Villemont and his rich American wife, the sensually beautiful, violently neurotic Anne, who knows only one thing surely: her child needs a protector. It must be someone not only tough enough to guard him against the unseen forces who menace him, but also resourceful enough to cope with a morbidly fearful little boy and his no less troublesome mother.
That was how Reno Davis, ex-prize-fighter, would-be writer, self-exiled American down on his luck in Paris, came to be the guardian angel of young Paul de Villemont, and how, like a fly innocently entering a spider's web, he found himself more and more tightly enmeshed in the web of deceit and danger being woven around him. Nor, as he soon learns, will breaking free of the entangling strands save him. Against all odds, the whole web itself must be destroyed.