Rose Hathaway, a half-human, half-vampire Dhampir, is training to protect her best friend, Princess Lissa Dragomir, a royal Moroi vampire. Both are students at a secret, secluded academy for Moroi and Dhampir. The academy trains Dhampirs to guard Moroi against the evil Strigoi—immortal and bloodthirsty vampires. Rose and Lissa share a deep psychic bond that allows Rose to sense Lissa's emotions and thoughts. After running away from the academy for over a year, they are caught by the imposing guardian Dmitri Belikov and returned to the academy.

Back at the academy, Rose struggles with her training while dealing with social challenges and mysterious threats directed at Lissa. As the two friends navigate complex relationships and uncover disturbing secrets about Lissa's unique powers, they must figure out who is trying to harm Lissa before it’s too late. Through their journey, they confront various dangers and form unlikely alliances, all while redefining their roles within their world. The stakes grow higher as they realize betrayal can come from the least expected places.