They both watched in fascination as the metal melted away, and black vapid smoke poured from the wound that the fang created. Harry saw, rather than heard Draco hiss in pain as what looked like hot blood began to pour from the cup and pour across his fingers while the room filled with the black billowing smoke. Harry stepped quickly further behind the protective glass but was relieved to see that the smoke hadn’t found its way through the small gap he had managed to squeeze himself through.