Sirius swallowed and approached the stool. Trembling slightly, he sat. Narcissa caught his eye from the Slytherin table and smirked at him. He looked away. He caught Remus and James’ eyes just before the hat was lowered onto his head, obstructing his vision.
“Ah! Another Black” said the hat in his ear. “Interesting. Very interesting. Now where to put you? You’re a loyal boy with a loyal heart, I see. And clever, oh yes. Very clever indeed. You have a flair for chivalry and bravery as well. Hmm… very interesting.”
Sirius wasn’t sure what to think. Loyal. Clever. Brave. Defining traits of every house except for Slytherin, according to Remus’ descriptions on the train. But… he was a Slytherin… all Blacks were… weren’t they?
“Not all Blacks” replied the hat. It could, evidently, hear his thoughts. “And no… no. Not Slytherin for you.”
Sirius felt his stomach churn. He felt his heart climb into his throat. Not Slytherin. Not… not Slytherin. Not Slytherin. He didn’t understand. His ears were ringing.
‘But my entire family is in Slytherin’ he thought at the hat.
“Not so. And even if they were, you are not a Slytherin. And now – where to put you?”
Sirius’ ears continued to ring, his head swimming. His entire foundation, everything he’d been told, was profoundly shaken.
“You are loyal and clever, yes. Very loyal and clever. But your bravery, your resilience, your daring and nerve… those will serve you well. Yes. Better be…”
And then, for the whole hall to hear:
Professor McGonagall removed the hat from his head. Sirius stood from the stool in a trance. He couldn’t hear the cheers from the Gryffindors. He didn’t notice the pulsing silence from the Slytherins. Somehow he found himself sitting at the Gryffindor table. People were patting his back, but he didn’t feel it.