Book 5 | Ch:06 - The Noble and Most Ancient House of Black

SPOILERS:

Harry, Sirius, and the Weasleys clean the Black house; Kreacher, the Black family house-elf, shows another darker side to house-elves; Harry is shown the Black family tree; and we learn that Sirius is not only related to the Weasleys and Tonks, but to the Malfoys and the Lestranges.