He was alone. Well, as alone as you could be with the entire wizarding public wanting your autograph and all of the muggles wanting to sue him for damaging some part of their property or another. His battle with Voldemort had taken him all over the world and he was sure that he was the only person to ever damage something that belonged to every person in the world.
Harry knew that he should be happy that he won the Last Battle and destroyed Voldemort, but in the process he had lost everyone he held dear. He was in his bedroom at Grimmauld Place and looked around him at the bleak and empty room. It held many memories. Memories of a past he'd rather not remember.
He heard a loud pop that echoed throughout the house, followed by many quieter pops on the main floor. Harry counted them. Twenty-three. Then he heard talking and assumed that the pops he had heard were the sound of people appearating. But he still didn't know what the first loud pop had been.
He decided that the best way to get rid of his visitors was to go down there, smile, hand out an autograph or two, and shoo them out so he could go back upstairs and sulk. But when he reached the bottom of the stairs, he saw something that made him go weak in the knees. "Mum, Dad, Sirius, Peter, Remus, Tonks, Mad-Eye, Dumbledore, McGonagall, Flitwick, Hagrid, Snape, Cedric, Mr. Weasley, Mrs. Weasley, Bill, Charlie, Percy, Fred, George, Ron, Hermione, Ginny!" When he reached Ginny he reached over and pulled her into a hug. "Ginny."
"Harry."
"How-How did you all get here?"
His mother answered him. "We were all eliminated in the battle against Voldemort. When you killed him, we were freed."
"Freed from what?"
"The Avada Kedavra curse does not kill, as was originally thought. Instead, it sends the victim into a dark existence. The only contact you have with others is if Avada Kedavra also eliminated them. And also the rare occasion when Prior Incantatum occurs, as you saw, Harry."
"Are you all alive now, or will you disappear again?"
"We are properly alive again. We won't disappear on you again, Harry."
Mrs. Weasley interjected. "When was the last time you had a proper meal, Harry? You look like skin and bones!"
"Um, I think it was last week."
"What have you been doing since then?"
"Well, um, I've been sulking and being non-social and mourning all of you."
"That's very sweet, Harry dear, but you've got to eat, too!"
"Yes, Mrs. Weasley."
"Please, dear, call me Molly."
"Yes, Molly."
"Very good, now, who would like some supper?"
There was a chorus of "Me, me!" from the surrounding people. Harry still couldn't believe it. All of the people he had been mourning were back, free. He had a mother, father, grandfather, girlfriend, and his two best friends again. He wiped away the tears he hadn't been aware had been streaking down his cheek. They were back. He had his family again.