Sirius spends ages pouring over the photographs in Harry's album. He points the people Harry hadn't known the names of, and even though all he can tell Harry is their names, it's something, and it means a lot to him. Sirius' smile lingers on his face the way the ghosts linger in the Hogwarts corridors sometimes - it's like he's forgotten he's even smiling, like he's forgotten he even exists for a few minutes as he browses through the photographs.

The ones he'd been sent are mostly of his mum and dad, but a few of them have Lupin in too, and he smiles at the picture of him.

"He's teaching here now," Hermione says quietly, "Lupin."

"He wanted to teach," Sirius replies simply, paging forwards, and then he grins. "Ah. You." It's a Muggle picture Jon Granger had taken of Harry and Hermione eating ice cream a few years ago, and Sirius smiles at it. The rest of the photos are of them, now - the photo Harry had clipped out of the Prophet last year, photos of Harry with the twins, of Hermione mid-argument with Padma Patil, and a photo of Harry talking to Snape. He'd liked that photo when Creevey had shown it to them - in the picture, Snape looks like he's almost in a good mood, arching an eyebrow as Harry says something vaguely insulting about Gilderoy Lockhart.

Sirius frowns at it. "Snape," he mutters. He taps the photograph as the picture Harry grins up at Snape, twisting his mouth in apparent disgust. Snape is about the same age as him, though, so Harry supposes they probably knew each other at Hogwarts.

"My head of house," Harry says, and Sirius lets out a noise that can only be described as a growl, flicking through the other photos. "You don't like him?"

"Snivellus," is the only response Harry gets, and he elects not to press any further. "None of the rat."

"I don't know any rats, Sirius," Harry says. "Sorry."

"No, no, no," Black says impatiently, and he pushes the album aside, his hand hovering over the map. Hermione reaches forwards, tapping it and activating it, and he gives her a grateful little smile as he folds the Marauder's Map out on the table. Harry wants to ask him questions, wants to ask who made the map, if Sirius knew the makers, what really happened when Harry's parents were killed... But he can't. Not yet. "He'll be here. The rat. He's at Hogwarts."

"Sirius," Harry says quietly, "Do you mean Pettigrew?"

"Yes. The rat, snivelling little- there." Black jabs at the little dot in the Gryffindor common room. "Pettigrew."

"But there's no one there, Sirius," Hermione says, and he groans, shaking his head.

"No, no. He's hiding. Look. Look." He goes silent for a few moments, eyes moving wildly as he tries to think, and then he says, "I'm dog. James was a stag. Him, him! The rat!"

"He's an Animagus?" Harry repeats.

"Yes! That's it. Animagus." Sirius makes a loud spitting sound, shaking his head firmly. "Should have known. Was always a rat, showed he was a rat. Need to get him, kill him." The words alarm Harry a little bit, so he pulls out the pack of cards he'd shoved into his pocket that morning, and he sets them on the table.

"Why don't we play a game, Sirius?" He furrows his brow, peering down at Harry, but then he nods his assent, and Harry deals them out. They're the funny cards he'd bought a while ago - a Muggle set with ridiculous wizards and witches as kings and queens, and occasionally Sirius will let out a bark of a laugh at an image he likes. Harry and Hermione stay with him for hours and hours, and when they finally leave, Sirius hugs them both like he's known them for a decade.

---

"Hi, Professor Lupin," Harry says lightly the next evening. The Marauder's Map has been returned to Fred and George, Sirius is settled in bed with The BFG to entertain him and the radio on in the background, and Harry just can't keep the smile from his face.

"Harry," Lupin says, offering Harry a small smile, and he taps a small trunk he has laid on its side beside his desk. "I've got another Boggart here. Thought it'd be better than bringing a real dementor in." Harry nods his head, and Lupin examines him for a moment, asking, "Having a good day?"

"A pretty great day, actually," Harry agrees. "So, what is the Patronus Charm?"

"Well," Lupin starts. "It's deceptively simple."

---

It becomes a routine for Harry. Every day, in the morning or in the evening, he'll creep out to the Willow to see Sirius, under the Invisibility Cloak to ensure he isn't seen. Sometimes, Hermione will go with him. Other times, it will be Fred or George. Most of the time, Harry heads down alone. Cooking for Sirius isn't hard, and by October he cooks himself, so that Harry doesn't have to worry that he'll only eat bread and apples all day: by mid-October, Sirius looks almost healthy, and he seems mentally healthier too.

It's obvious to Harry that there's still a lot wrong, but Sirius can hold a real conversation, and Harry's finally able to actually talk to him. Harry tells him about his day, and Sirius actually responds; more excitingly, Sirius talks right back. He tells Harry how he liked this book or that article in the Prophet, or what he heard on the radio yesterday, and it's- It's strange. Talking to Sirius feels like talking to an imaginary uncle, one that doesn't despise him, and when Harry voices the thought he laughs.

"Well, I'm your godfather, Harry," he says one early afternoon, and the thought rings through Harry's entire being. It seems completely right, somehow.

"Really?"

"Really," Sirius confirms, giving a nod of his head, and he shifts his position in the chair he'd conjured a few days ago before he says, "I'm not surprised no one told you. I wouldn't have."

"Will you tell me what happened?" Harry asks quietly. "That night?" Sirius slowly inhales, gripping at the arm of the chair he's sprawled in before he releases it: he wears some of Percy's old trousers and a yellow jumper, a collared shirt underneath. Harry's first Hogsmeade trip is next week, and Harry has plans to buy him some more things to wear. This is the first time Harry's actually questioned Sirius on the subject, but Sirius doesn't react that badly - he fidgets a little, but he doesn't explode. Harry feels like he might have, a month ago.

"Firstly, you have to understand, Harry. At school, me, James, Peter and Remus - we were the best of friends. There were crucial things we bonded over... Have I told you it was us that made the Marauder's Map?"

"You hadn't mentioned that, actually," Harry says wryly, and Sirius laughs.

"Well, we did. We bonded so closely, and upon leaving Hogwarts, James and I became Aurors, but... There was a prophecy. A prophecy that talked about you, and Voldemort: that's why he pursued you, tried to kill you when you were a child. There was someone else-" Sirius focuses for a second, pressing his lips together, but then he shakes his head. "I don't remember. But it could have been another boy, and it wasn't: he chose you. We hid James and Lily under a Fidelius Charm. Have you heard of it?"

Harry shakes his head. "It hides knowledge from outsiders, and only the Secret Keeper can reveal that knowledge. Lily and James were hidden in Godric's Hollow, but even if you were looking into Lily's eyes, you couldn't have known she lived there without the Secret Keeper telling you. We thought-" Sirius' face becomes a mask of pain and grief for a second, and then he says, "We thought Remus was feeding information to Voldemort. We thought he was betraying us, and I believed that were I to be made Secret Keeper, they'd come after me first. I thought I was too obvious, so we chose Peter."

"And it was him. It had been him all along - I ran to the home in Godric's Hollow, saw James' body on the floor, saw Lily in front of your crib- And Merlin, Harry, how you cried. There was blood all over your face, and I picked you up, held you, tried to stop you crying... But you were alive. I brought you outside to my bike, and Hagrid - you know him, Hagrid? - he said he needed to take you. Well, I let him - I gave you straight over, because I needed to go after Pettigrew. Hell, I told him to take my bike, even. And I went after him."

"People celebrated that night," Harry murmurs. "Were you the only one...?"

"No one else knew. I tracked him to this Muggle street, and he blew up the whole street, cut off one of his fingers and dropped into the sewers."

"As a rat."

"As a rat." Sirius shakes his head slowly, and says, "I was crazed, hadn't slept in days- I couldn't do anything but laugh. All I could do was laugh."

"I'm sorry," Harry murmurs, and Sirius meets his gaze. His eyes look so old, Harry thinks, so much older than they should. "And escaping?"

"I saw him, Peter. In the paper. This family, they'd won money, gone to Egypt. This boy, this one boy- he had him in his hands for the photo." Sirius lets out a low, sharp noise of frustration, shaking his head. "I've not gone into the castle yet - but I could, Harry, I could-" Harry interrupts him.

"Family...? What, you mean the Weasleys?" Sirius shrugs. "Sirius, Fred and George - they're Weasleys. They just got back from Egypt this summer, and their brother, Ron, he has-" Harry goes abruptly silent. He feels stupid for having waited so long to ask Sirius about this, because all that time, Pettigrew has been in the Gryffindor common room. "He calls him Scabbers. I've got to go."

"What?"

"I'll have you pardoned by tomorrow night," Harry promises, running out of the tent. "I promise, Sirius!"

---

Harry couldn't possibly luckier than he is in this moment. As he enters the great hall, lunch is just beginning to finish up, and he can see Ron Weasley at the Gryffindor table, trying to get Scabbers to eat, but Scabbers just keeps trying to struggle free: Harry runs up to Snape at the table. He's heard Sirius talk a little about Snape, about how much he hates the man, and how it was always mutual...

"Sir," Harry says urgently, "What should I do if I believe there's an unregistered Animagus in the castle?" Snape stares at him, taking a slow, measured sip from his drinking glass. Harry can see Flitwick and Sprout craning to listen, obviously curious, but they don't interrupt.

"You ought report it, Potter, to a member of staff."

"And what would you do?" Snape sets his jaw.

"Potter, barring Professor McGonagall, there are no Animagi in the castle."

"I bet you ten Galleons that there is one, sir." Sprout does her best to hide a snort of laughter, and Snape shoots her a glare that only serves to make her laugh more. "I think he's helping Sirius Black." Something flashes in Snape's eyes, and Harry knows he's used the right strategy: even without Sprout and Flitwick there, Snape would be willing to listen.

"Do you, indeed?"

"Isn't there some way to tell?" Snape sighs, doing his best to look put-upon, but Harry can see the slight tension in his jaw and his neck.

"Oh, humour the boy, Severus," Flitwick says, offering his coworker a gleaming grin, and Snape "reluctantly" moves to stand, scowling down at Harry.

"Where is this Animagus, Potter?"

"Right over here, sir, at the Gryffindor table."