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The Key and the Culprit
He slammed the vial with the robin's egg blue stopper on Auror Potter's desk. "Here it is."
Harry blinked from the sandy substance to Severus's serious face before glancing at Elaine, who hovered at the doorway.
"Uhm, alright… er… what is it?"
Severus rolled his eyes, "Use that prodigious education Potter. It's the antidote."
Potter touched the stopper reverently, his eyes glowing.
"One grain dissolved on the tongue. Wait twenty-four hours, if there is no change a second may be used," he turned in a billow of robes and offered Elaine his arm.
"But wait, Professor —what about the perpetrator?"
Robin's Egg, #91