Twentyone days

AU / Death Eaters besiege Hogwarts. A spell from Dumbledore is going astray. A cauldron explodes during potions class. And the old castle enfolds its own magic. Can some students survive the next twenty-one days? How will they deal with everything thrown their way due to "the tragedy of Hogwarts" as reporters call it? Accompany them on their struggle to stay alive ... thanks ...