The case begins when Gabriel is invited for a weekend at the home of a currently dethroned royal scion. Grace is delighted, assuming that at last they're moving into the kinds of circles a family like the Ritters ought to hobnob with. But it turns out that the 'Prince's' motivation for inviting Gabriel was not a social one. He has a new infant son and is concerned for his safety because the Prince's family has been plagued for generations by what seem to be a secretive sect of vampires.