This was the 18th moon since he had arrived.
He knew because this was how he counted the months now; how many nights Remus transformed alone. Sirius knew he was going mad because he could hear Remus's screams from his barred window. 18 long moons. 18 transformations without padfoot to aide him. How was he coping by himself? Did he register with the Ministry to protect everyone? Did Remus even still live in London?
As far as Sirius could guess the moon had been out for about six hours. Remus would be long lost to the wolf by now. With a hoarse, humorless laugh, Sirius wondered if the Wolf remembered him. His laugh quickly turned into a hacking cough that wracked his entire body and tore open his lungs. Soon, Sirius was reduced to a slumped pile on the floor of his cell. He clawed his way up to a standing position so he can peer out the bars in his window towards the moon once again. The sight of it used to bring him... not joy exactly-- how could it be joy when the boy he loved was bent over in pain-- but, relief from the human world for a while. Now, the glowing body in the sky only brought on the empty, wallowing grief that washed him with apathy nearly every night.
He turned away from the outside wall and slid to the ground so he didn't have to look at it any longer. Sirius let his head fall backwards to the wall with closed eyes and the hint of a sigh. Sometimes, if he really tried, he could still taste Remus on his lips. He could feel the touch of his long fingers tracing patterns all down his back and gripping Sirius's hair. He could sense the warmth of the boy's embrace on the long nights they spent awake waiting for James to come back from a mission. No more of that. Prongs was gone. So was Moony. So was Padfoot. Wormtail was dead to him. Or should have been. Sirius stifled a sob that climbed its way into his chest. He would have pressed a hand to his eyes, if he had had any tears to cry.
Dammit Padfoot this is your fault. You don't get to cry about it.
Sirius could sing; he wasn't great at it, but he could do it. Mostly he would sing because Remus liked to hear it. He would always say it made him feel like they were the only two people who mattered in a room. Sirius would always say that Remus was going soft. Sirius loved when Remus said that. It made him feel like the other boy may be on to something. Sirius would sing from time to time in his cell. While it made him indescribably sad, at least it tethered him to the outside world. Mostly it just made him wish he were dead.
The moon shone through his bars, casting elongated shadows onto his floor. The air was so still, and his prison was so high up that the only sound was the moaning of tortured soul after tortured soul. Soon he'd be one of them...
"You are my sunshine,
my only sunshine"
His voice was cracked from disuse and dehydration, but the familiar lyrics slipped off Padfoot's tongue like water off an umbrella.
"You m-make me happyyy
when skies are grey"
Sirius's eyes drifted shut as he let the memories of early mornings with moony envelop him. He always knew when Remus was awake first, because he would sing quietly to himself in his slightly off-kilter way when he thought Sirius was asleep. Sirius loved it. And sometimes, when they'd both had too much to drink, Remus would take him in his arms and sing into his ear as they "danced" around their flat. This was his favourite.
"You'll never know dear
How much I loved you"
His voice lasted until 'loved' before Sirius could barely speak. The emotions which he could hardly ever feel anymore were bubbling up to the surface and threatening to truly overwhelm him this time. He didn't have to close his eyes to see Moony's face looking at him anymore. Remus was just as beautiful as he remembered.
"Please don't take
my sunshine away"