Draco let Potter take a day to familiarise and memorise his childhood home, storing each room in his mind palace, each room having the five main objects within it. Draco took this time to tend to his plants and to the base potion that would, hopefully, produce the Philosopher's stone.

The ingredients had been difficult to obtain (as was shown by the fact that he was growing the plants himself), but the brewing of the potion itself was almost impossible. First of all, it was written in a shorthand Draco could hardly read, so he'd had to transcribe it; secondly, he'd had to find rare varieties of stirring sticks and cauldron materials in order to be able to brew the cauldron with as few lethal reactions as possible. He'd avoided any so far, but the most dangerous part was when he added one of Viv's leaves, ground up into a mush, mixed with a drop of his own blood- red blood, pure and young; tainted, as all humans are, the instructions had read. The blood, if not matching the instructions, could very easily explode and ruin all attempts of the potion.

Potter still brought him food; he'd been sneaking food in from the kitchens (he'd tried asking the Room for some, but it just didn't taste quite as good) and had taken to cooking up lunch for Draco and himself. It forced Draco to take a (well-needed) break from his potions and plants, and it allowed Potter a break from his memorising of his house.

When he had finished with the physical layout of his house and was able to recall every room and the items within it as quickly as Draco could think of them, Draco deemed him able to move on.

"The next step is to start adding people, for your purposes, I think," Draco told him. "You want to relax, right? Have a place you can get away to? Well, wouldn't you like your friends there? And you could add dead people- like Diggory, or Lupin, or that godfather of yours. If you know them well enough, you can add them. You could even add your parents."

Potter's eyes had widened, and his lips had parted. "How?"

"You know how you put all the items in your rooms?" Draco asked.

Potter nodded.

"Well, do that but with people. Get out of the Room of Requirement, get back into Hogwarts; start going to lessons and all again. But pay attention to your friends. To anyone you want to put into your house, really. Memorise them. Little things they do when they're bored, how they fiddle, what they like to eat, their speech patterns; memorise them."

"Oh, um, okay. But- er, I mean- how- what do you mean?"

Could Draco have said it better? Gryffindors, honestly. Draco sighed. "Alright, Potter. You blink when you're confused; you get quiet after a nightmare; you trace your scars when remembering them or what gave you them; whenever someone mentions something you don't like, you close off completely- it's actually a little scary; when someone brings up a dead person who fought for you, you turn your head a little to the left, like you're trying to turn away from the conversation. You're almost always looking over your shoulder; when you go round a blind corner, you hesitate a moment; you stand in your duelling position, with your right foot in front of your left-" and Draco cut himself off there, because he was revealing that he knew far too much about Potter, and Oh, Merlin, was Pansy right?

Thankfully, Potter was oblivious and thought Draco had just been listing off his attributes, not revealing all the things he'd noticed.

"Right, I see. Thanks."

Draco nodded his acknowledgement. "So, once you memorise someone, you pick a room that they'd most likely be found in- so, for your Weasel, probably the kitchen-" Potter made a sound of protest, but Draco smirked and moved on- "And you put them there, in your home in you mind, doing something- always doing something, because you'll remember movement better than most other things. So, put Granger on the sofa, reading, for example, rather than having her stand around doing nothing. Have Lovegood sitting upside down reading the Quibbler, rather than just pointing at something and smiling. The crazier and more absurd, the better, because you're more likely to remember the crazy thing in the future..

"You have to know the person who you're putting in your mind palace well enough to be able to pretty much know what they'd say to a certain situation. Take the Weasel again. If faced with a group of Acromantulas, he would scream. Don't look at me like that, you know it's true. So you have to be able to predict their actions; when you retreat to your home in your mind, you will go to whoever you need, and they will help you. But you have to think of how they'll help you, because they're in your mind.

"Really, people are supposed to be there to prompt you, to make you think a certain way; so a Hufflepuff might be there to make you think more kindly, a Gryffindor to make you braver. A Ravenclaw to make you smarter, a Slytherin to help you achieve your goals. So, that's your mission for the next-" he glanced at the potion- "two days. After that, I'll need you to supervise me with the potion in case something goes wrong. We had Severus' portrait down in the dungeons, but here the portraits are far more limited, I believe. So, off with you. Go learn some people, inside and out."

. . .

Potter returned halfway through the second day.

"Need my help, Potter?" Draco asked as the door to the Room creaked open.

"Actually, yeah," Potter said.

"Go on, then."

"Er- can I ask you some questions?"

"You just did."

"Right. Well- er-" And Potter proceeded to ask Draco what felt like a thousand questions, varying in topic and seriousness. Some were about his friends, some for his family; some were what-would-you-do-in-this-situation type questions; some were more personal, more about his thought processes and emotions. Some were about his qualities as a person; how he acted around people, how he talked to get what he wanted. Draco closed off on a couple, but had no problems with the rest, until- "What are your eating habits like?"

Draco had been trimming Viv's twigs back, pampering her leaves and not really paying attention.

"Well, I get hyper-fixated on some things. I'll forget to do everything else, like sleep and eat, because I'm so used to just working on something, and not allowing myself any basic needs until it's done. Guess it's a habit now." Draco didn't see Potter's eyebrows shoot up. "Sticks pretty easily, too. After I first developed it, back in sixth year-" he didn't see the way Potter's body went tense and still- "I couldn't eat much except water on a day-to-day basis, 'cause my body was so used to receiving so few nutrients, getting so many from a full meal made me sick."

"Draco," Potter said, and Draco got a double shock to his system. Firstly, he'd forgotten Potter was there. He would never had said that about himself, revealed such a weakness, if he'd remembered someone was listening. Stupid! Second- 'Draco'? What happened to 'Malfoy'?

His head shot up, staring at Potter like a deer caught in headlights.

"Draco, when was the last time you ate?" His voice was inquisitive, calm- but Draco had analysed Potter's every move for as long as he could remember.

He was unbelievably close to bursting with rage.

What did he want Draco to say?

"Um-" Wait, actually- when was the last time Draco had eaten? Not today, certainly, and he'd skipped dinner and lunch at the Great Hall; had he even gotten something from the House area of the Room? His brow furrowed as he thought, and when his stomach groaned, Potter stood.

"Draco," he said again, and this time his voice was soft. "When was the last time you ate?"

"Well- probably- when you last made lunch?"

Potter's eyes went dark. Uh oh. They hadn't done that in a while. And last time Draco had seen that look directed at him- oh. Sixth year. Girl's bathroom.

Taking that into account, it was entirely reasonable that Draco immediately stiffened- Potter flinched back in surprise- and Draco took the moment to bolt out of the Room like a frightened bunny.

He kept running after he was out of the Room- he knew he had a few seconds that Potter would spend standing still, blinking, and he used them well. He sprinted down the corridor, and, remembering Potter's Map, decided that he would leave Hogwarts grounds at once. But where to go? Where would Potter not think to find him? He couldn't go home, couldn't go to anywhere in Hogwarts- where could he go?

Oh- there was an idea. But could Potter get in? No, he couldn't. He wasn't a descendant of that family. He probably didn't even know the pace existed. Yes, Draco could hide there.

He made his way quickly out of the school grounds, and then Disapparated.

He appeared in a dismal grey street, somewhere in London. The sky was a blanket of grey, and the chill in the air promised a shower of rain soon. Draco shivered- he was only in his school robes- and stepped forward as a house emerged from between two others. His mother had brought him here when he was very little- the House of Black, she'd told him it was. For years he'd thought it was called "Grim Old Place", for while it was majestic in its pure-blooded splendour, it was grim, and old, and grey. It was hidden from the muggles by a Fidelius charm. He wondered who the Secret-Keeper was nowadays.

He stepped inside. He remembered this house; though he'd been young during his first visit, his mother had brought him back here every now and then, showing him her childhood home.

He walked over to where the family tapestry hung on the wall, a few scorch marks of disappointing children burned off across the fabric. Near the end, he saw his own little portrait. He turned away.

The place reeked of dust, grime, and mothballs. Draco set about making himself a nice cup of tea to drink while he let his mind wander- avoiding any thought of Potter or sixth year or Voldemort or- well, he thought about where he was. This old, abandoned building in muggle London, once a place of magnificent splendour, now a run-down abode devoid of life.

Number 12, Grimmauld Place.