Harry blew the whistle and the TARDIS materialised.
The Doctor stepped out, wearing his standard blue suit, with long coat.
Harry smiled, properly, for the first time in he didn't know how long. The Doctor saw him, and grinned.
"Harry!" he said, his voice high pitched and warm. "How's it going - hang on," he noticed Harry's expression for the first time, his smile uneasy now. "That's a sad smile, that's not a happy smile, why are you sad, what's happened?"
Harry took a breath, and spoke.
"It's been about a year since I last saw you, and a lot has happened," he explained. "Dumbledore is dead, and has been for a few months; Voldemort's taken over the Ministry. Me, Hermione and Ron are now on a quest to find a way to kill him."
The Doctor had stopped smiling when Harry had said "Dumbledore is dead."
"Why didn't you call me earlier?" he asked.
"To be honest," Harry said, "Hermione was all for calling you at the start, but me and Ron didn't want to get you involved."
"Well," said the Doctor, "I'm involved now. What can I do to help?"
Harry held up the Locket Horcrux. The Doctor stared at it for a while, then spoke.
"Hmmmm," said the Doctor. "I think you should get the others, and come inside the TARDIS. Go get them."
"Do you know what it is?" asked Harry in disbelief. The Doctor was a good guy, how could he know about Horcruxes?
"I know the principals," he said. "I did a lot of research into the wizarding world while I had the chance. Go get the others, I'll take you with me."
Harry went, taking the Horcrux with him. What the Doctor hadn't told him was that the Horcrux had been speaking to him, slowly and malevolently, from the moment he saw it. He could still hear its voice in his head...
Murderer, killer, betrayer, death becomes you, you lock the Master up and yet you are just like him... you seek power, Doctor. They are your playthings, nothing more.
He had argued silently with the presence in the locket.
I have done much good. All I have ever tried to do is the right thing... and you are no judge of me, Voldemort.
Perhaps, but I never try to pretend I am anything more or less then pure evil. You hide behind morality, justify slaughter, erase beings from existence... a wonder she ever loved you...
The Doctor's precious Rose... does Miss Granger even know about her? Do you even talk about the woman you lo -
You aren't worthy to lick the slime of her trainers. NEVER speak of Rose to me. Ever.
Ha, ha... I made the Doctor mad. I wonder... if I was to look deeper, how mad you would become...
At that point, Harry had run off to get the others, and the Doctor breathed easier.
But in his mind, another voice sounded.
He speaks the truth, Doctor. A man cannot fight all these monsters without becoming the greatest monster of all. One day, you will fall.
And I will return to see it.