When Dobby brought Harry to Douglas's house the next day, Harry discovered that there was a large black dog in the house.
According to Douglas's plan, he could not reveal his true form in front of Harry until Harry discovered the truth himself.
Harry asked Dobby curiously:
"When did my cousin get a dog? It wasn't here when I left yesterday."
Dobby stammered, not daring to speak. He did not want to lie to Harry Potter, but Douglas had instructed him to keep this from Harry for now.
"Dobby... Dobby... Good morning, boss!"
Seeing Douglas emerge from the bedroom, Dobby hurriedly greeted him, then quickly left to do the housework.
Douglas explained:
"Well, I picked up a stray dog last night. His name is Padfoot."
Harry glanced at the black dog when he heard the name. What a strange name.
Besides, Harry kept feeling that Padfoot looked at him strangely. It was a very complicated look. Harry greeted him politely:
"Good morning, Padfoot!"
There was no telling what chord those words struck in Sirius, but the thin, large dog suddenly burst into tears, staring at Harry and whimpering.
Startled, Harry hurriedly said:
"Professor, your dog's crying! I didn't hit him!"
For the rest of the day, Harry kept finding the dog strange. He kept feeling that the dog looked at him as though he were a brother.
And while Harry did his homework, the dog curled up beside him, quiet and well-behaved, but staring at him the whole time.
He had reason to suspect that his cousin had found a dog specifically to watch him do his homework.
After a week of Sirius being a dog by day, watching Harry do homework, and a man by night, doing research with Douglas, something happened.
Mr. and Mrs. Granger brought Hermione over