The prince of Ombria is dying, and his mistress Lydea is telling his son and heir, Kyel, tales of the other city, the shadow city, until he has died, and Dominia Pearl, the mysterious Black Pearl who dabbles in sorcery and has a pirate fleet, and takes over the regency once the prince dies, has Lydea thrown out into the street. She manages, somehow, to escape back to her father's tavern.
Mag watches and helps her. She is the waxling of a sorceress, Faye, who told her that she made her out of wax, except one day, when Mag accidentally swallowed a heart that Faye had sent her to deliver, and she had realized that she was, in fact, a human being.
And then there is Ducon. The late prince's sister's illegitimate son, of an unknown father. He wants to protect his cousin from Dominia Pearl, but intriguers at court, since all the other heirs are too old and weak to thwart Dominia Peral, want him to kill Kyel and seize the throne himself.
Intrigues ensue. Adventures and mysteries in the city and the shadow city, and in the underworld. Charcoal and poison. A child captured in a library, and a disguised tutor. A much loved child is made a foundling. A tutor tries to help Kyel. Faye shows a knowledge-mad man the ghosts of the city. Mag brings Lydea her shoes and tries to stop an assassination. . . .
All this in McKillip's gorgeous, lyrical prose. Which is, in this book, never so gorgeous as to obscure what the heck is going on, which (alas) it sometimes is in other works of hers. I think it's my favorite McKillip.