The illegitimate son of a peasant, Rion of Tryferos has very limited prospects with only one remarkable talent: when he plays the lyre, he ushers in the supernatural balm of peace to all who hear. This turns out to be his ticket into the palace, where he nightly plays for the restless, rejected king. King Hector of Tryferos is paranoid, because he knows his days on the throne are numbered. What he doesn’t know is that his anointed successor is Rion.

Princess Genevieve is a spare to the throne of Mageia, shunned by all but her mother out of fear of her magical gift: she possesses the power to manipulate the thoughts and desires of those around her. But Ginny would do anything just to be normal. When a fulfilled prophecy of her mother's untimely death also foretells that Ginny will ascend the Mageian throne, Ginny wonders whether she has any control over her own fate at all, or whether everything is predetermined.

Both Rion and Ginny are drawn to the forbidden Caves of Glass at the icy pinnacles that border their two perpetually feuding nations. According to legend, the Caves are either a place of strange forbidden magic, or else a place where all deception is stripped away, leaving only clarity and truth in its wake. As Rion flees for his life and Ginny struggles against her destiny, in the Caves of Glass, they find both each other, and themselves.