It is in the full moon that Sirius finds one of the last pleasures that fate sees fit to afford him. In the dying part of him he feels guilty for enjoying what gives his lover so much pain, but he banishes the guilt away. He will not deny himself one of the few things that give him joy.
He watches Remus change from man to wolf with a perverse pleasure. The agony that screams inside him made flesh on the form of another is almost delightful. He feels the old tides of vengeance wash upon him, and once he has assumed his second form he feels whole.
Being Padfoot does to him what ten consecutive bottles of Firewhiskey cannot: it brings his youth back to him. Padfoot has not changed. His body is still lithe and firm, ready for action. Sirius's mind is under a thick film while he possesses his dog form. He acts on instinct, without the burden of responsibility or guilt. It also brings him closer to Remus.
The wolf who is not really a wolf and the dog who is not really a dog tussle through Sirius's house carelessly. Sirius thinks that Remus feels the same kind of abandon and elation when he is a wolf that Sirius feels when he is a dog. But Remus lets his guilt conquer him. He has lived too long loathing his alter form to ignore the pleasure he now derives from it, so at all other times he insists on being infuriatingly human.
With the moon full Sirius has an excuse for being Padfoot. If anyone were to walk by they would see him playing with Remus and they would think it kind of him to comfort a man turned monster. But when Remus is not Moony and Sirius is Padfoot they look down their noses at him and scowl. Foolish Sirius playing his stupid games.
Molly is the worst. If she catches him as a dog without Moony she gives him a speech about not avoiding his problems and setting an example for Harry.
"Harry is not here," he wants to say. "Harry is never here. Harry does not want to be here." But he cannot speak as a dog except to whimper, which he does, under his tail, as Molly walks away.
Remus never says anything when he finds Padfoot curled up on the bed, except for the times he asks him to turn back into Sirius so that they can perform a mockery of sex.
It is awful, the things they do to each other in that bed. Sirius knows Remus wonders why he bothers. He knows Remus thinks about how it used to be, how just by looking at each other shivers would run down their spines. It is not that way anymore, and Sirius knows it breaks Remus's heart.
They can't look at each other when they have sex anymore, for if they do all Sirius will see is the newer scars and all Remus will see is the ghost of a man he once loved. They used to call it making love. Sirius can't call it that anymore. All they are making is an attempt to feel alive again, and they fail every time.
There are times Sirius wishes for death. He thinks of what would happen if his younger self saw him now and he feels a terrible shame rise in him and wonders the point of living at all. Harry has others to motivate and love him and Remus is too strong to need him. But then he thinks of what his younger self would say if he took the cowardly way out and the shame is doubled. There is no point to his life or death.
When he first arrived at his childhood home he was filled with many deep and powerful longings. He longed to know his godson and earn his trust and love. He longed to feel the way he once did of Remus, to feel that fire that warmed his very soul. He longed for his freedom; he wanted to smell the rain and the trees and the grass and the fresh air. It was when this last longing eclipsed the others that Sirius knew he had finally lost himself; he would not have chosen that road in the past. The dementors had nothing on what Sirius did to himself.
He knows who he was back then. Remus does not think he can remember clearly, he believes that Azkaban had taken his past and hidden it from him, but Sirius remembers everything. Every memory is his to keep and suffer from.
He remembers James most clearly; for these are the memories he seeks the most comfort in. Memories of Remus are tainted by what Remus has become, so he looks for no solace in those. James is unobstructed and unparalleled, even by Harry. For a while Sirius fooled himself into think Harry was James reincarnate, but he is not. No one is James.
In his mother's old room he babbles like a madman to Buckbeak. "James would understand," he says. "James would comfort me. He would know exactly what to say. James would understand. James would make everything right. James loves me. I'm his best friend, did I tell you? Best man at his wedding. James would understand."
When his voice gets too hoarse to discuss James any longer Sirius seeks comfort in other ways. Mostly, he stares into the single deep red eye of the Firewhiskey bottle and asks it questions.
How could I make so many blunders in one lifetime? How can I ever forgive myself? Should I forgive myself? Why have I become totally and utterly useless?
He never gets any answers, but he keeps trying anyway. Slowly the bottle lowers its eyelid until there is nothing left of it. So, Sirius takes out another bottle and asks it the same questions. He does this until he falls into a deep and restless sleep.
He has become weaker, injuries befall him more easily than they used to. Where his body was once firm and sturdy it is now just several feeble limbs tied together with little more than sheer willpower.
One day he finds Buckbeak bloodied and howling and he thinks he has passed on this weakness. He has finished cleaning him up when he hears a commotion downstairs. They are yelling for him to come downstairs, to hurry up.
He stands and he feels horribly old, but each step toward the other members of the Order takes years off of him. He feels like Padfoot, he is running on instinct. A powerful feeling is building inside of him and he knows he will be outside again soon. Free to smell the earth and free to fight for what he believes in, so that he may be himself once more. Free also to exchange deep glances with Remus, and to send shivers down each other's spines. It is sinful, to do things like this with each other in desperate situations, but when weren't things between them sinful?
There is joy in his limbs as he rushes towards the front door of the house. He is filled with purpose, his life has meaning again, he is Sirius Black once more.
But despite this he sees the door yawn arch-like over him, and he knows it means his doom.