The house-elf froze in his tracks, stopped muttering, and gave a very pronounced and very unconvincing start of surprise.
“Kreacher did not see young master,” he said, turning around and bowing to Fred. Still facing the carpet, he added, perfectly audibly, “Nasty little brat of a blood traitor it is.”
“Sorry?” said George. “Didn’t catch that last bit.”
“Kreacher said nothing,” said the elf, with a second bow to George, adding in a clear undertone, “and there’s its twin, unnatural little beasts they are.”
Harry didn’t know whether to laugh or not. The elf straightened up, eyeing them all malevolently, and apparently convinced that they could not hear him as he continued to mutter.
“…and there’s the Mudblood, standing there bold as brass, oh, if my mistress knew, oh, how she’d cry, and there’s a new boy, Kreacher doesn’t know his name. What is he doing here? Kreacher doesn’t know…”
“This is Harry, Kreacher,” said Herrmone tentatively. “Harry Potter.”
Kreacher’s pale eyes widened and he muttered faster and more furiously than ever.
“The Mudblood is talking to Kreacher as though she is my friend, if Kreacher’s mistress saw him in such company, oh, what would she say—”
“Don’t call her a Mudblood!” said Ron and Ginny together, very angrily.
“It doesn’t matter,” Hermione whispered, “he’s not in his right mind, he doesn’t know what he’s—”
“Don’t kid yourself, Hermione, he knows exactly what he’s saying,” said Fred, eyeing Kreacher with great dislike.
Kreacher was still muttering, his eyes on Harry.
“Is it true? Is it Harry Potter? Kreacher can see the scar, it must be true, that’s the boy who stopped the Dark Lord, Kreacher wonders how he did it—”
“Don’t we all, Kreacher,” said Fred.
“What do you want, anyway?” George asked.
Kreacher’s huge eyes darted towards George.
“Kreacher is cleaning,” he said evasively.
“A likely story,” said a voice behind Harry.
Sirius had come back; he was glowering at the elf from the doorway. The noise in the hall had abated; perhaps Mrs. Weasley and Mundungus had moved their argument down into the kitchen.
At the sight of Sirius, Kreacher flung himself into a ridiculously low bow that flattened his snoutltke nose on the floor.
“Stand up straight,” said Sirius impatiently. “Now, what are you up to?”
“Kreacher is cleaning,” the elf repeated. “Kreacher lives to serve the Noble House of Black—”
“And it’s getting blacker every day, it’s filthy,” said Sirius.
“Master always liked his little joke,” said Kreacher, bowing again, and continuing in an undertone, “Master was a nasty ungrateful swine who broke his mother’s heart—”
“My mother didn’t have a heart, Kreacher,” snapped Sirius. “She kept herself alive out of pure spite.”