Harry meets his twin sister. She’s coming to Hogwarts from a secret orphanage established by Dumbledore after the first war. There’s just one condition: her true identity must be concealed by an Unbreakable Vow.

Harry enters his sixth year at Hogwarts. A young promising auror, the new Care of Magical Creatures professor, and his sister may be the key to defeating the Dark Lord. That is, if no one breaks their vow.