When the Second Wizarding War erupts, Dumbledore and McGonagall summon a forgotten force — a witch so powerful that even Voldemort once fled from her. She is ancient, immortal, feared and revered in equal measure… And she happens to be Severus Snape’s mother, though he knows almost nothing about her past. Her return to Hogwarts changes the balance of the war — and forces Severus to face the fact that he didn’t inherit his darkness from his father. He inherited it from her.