When Harry got off the train at the end of the school year, he wanted to go to Grimmauld Place. But it was a few days before he actually got there.
He had sent a letter to Tonks asking to go back. She told him it would be a while. When she came to pick him up, she scared the Dursley's half to death. Finally, they got to leave.
The first thing Harry wanted to see was the Black Family Tree, but the Order took him to the backyard first. They showed him why they couldn't come get him for a while.
In the backyard, the Order had put up two stones. As Harry got closer, he realized they were markers. On one was the name Sirius Black, and on the other, JoAnna Bouchar. "This way, they'll always be remembered by any one in this house," said Tonks.