In a remote, mountainous area of a Maui forest near Haleakala volcano, the naked body of a young woman is found hanging from a tree. The nostrils, mouth, and lungs are packed with lava sand. Her hands are bound in twine. Her feet are charred and blackened, suggesting a fire-walking ceremony. For Detective Kali Māhoe, all signs point toward ritual torture and murder.

But Kali's investigation leads her down a winding trail of seemingly unconnected clues--from the hanging tree itself, a rare rainbow eucalyptus, to rumors of a witch haunting the high areas of the forest, to the legend of the ancient Hawaiian sorceress Pahulu, goddess of nightmares. Casting a shadow over it all--the possibility of a Sitting God, a spirit said to invade and possess the soul. Aided by her uncle Police Captain Walter Alaka'i, Officer David Hara, and the victim's brother, Kali embarks down the darkest road of all. One that is leading to the truth of the mountain's deadly core and a dark side of the island for which even Kali is unprepared.