Coils - Barbara Ann Wright

Cressida loves Greek mythology, tales of gods and monsters, but she knows they aren't real no matter how awesome it would be to meet the beautiful women of myth. When her aunt June disappears, Cressida realizes the other members of her family aren't so rational. June's notes point to a possible entrance to the fabled Underworld before they cut off completely.

Following June's footsteps leads Cressida into a world she knew only as legend, a place of marvels and danger, where the living are highly prized by the dead. Desperate, Cressida turns to Medusa, a demigoddess who's been maligned by myth, but everything in the Underworld comes with a price. Medusa is more than willing to help find June, and all it will cost Cressida is one little murder.