The story picks up two months after the events in the first book. The opening chapter is narrated by Kartik, who has been brought before a council of the Rakshana. He is told that by destroying the Runes, Gemma released the magic, making it available to all the creatures in the realms, including the evil Circe and her allies in the Winterlands. Kartik is charged with helping Gemma find the Temple in the realms, where the magic can be bound by the Rakshana, and when that is successfully completed he is to kill her.

The rest of the story is narrated by Gemma, in the present tense. Gemma is told by Kartik that she must find a "Temple" in the realms to bind the magic "in the name of the Eastern Star"; unbeknownst to Gemma, saying that line would give the Rakshana the power.

It has been a year of change since Gemma Doyle arrived at the foreboding Spence Academy. Gemma has relied on an unsuspected strength and has discovered an ability to travel to an enchanted world called the Realms, where dark magic runs wild. Despite certain peril, Gemma has bound the magic to herself and forged unlikely new alliances. Now, as Gemma approaches her London debut, the time has come to test these bonds.

The Order—the mysterious group her mother was once part of—is grappling for control of the Realms, as is the Rakshana. Spence's burned East Wing is being rebuilt, but why now? Gemma and her friends see Pippa, but she is not the same. And their friendship faces its gravest trial as Gemma must decide once and for all what role she is meant for.