The night was dark. Darker than usual. It's been one year since he got accused of killing his friend, no; his brother. Not by blood but by heart, mind and soul.
In rage Sirius throws his fist against the cold, black bars of his cell while letting out a gutwrenching scream. And one more. And one more.
He keeps on punching the still so solid poles of his prison. Sliding into his already so familiar madness he starts to throw his whole body against it to feel at least physical pain to push away the war in his head while screaming until his voice should've given up.
And even then he couldn't stop. In the flow of loosing control about it all he lets out the few breaths he can as his vision turns red.
Just then, when he only hears the rushing of blood in his ears he perceives the angry voices of his cell neighbours; »Shut it up blood-traitor, that filthy mudblood and it's twink of a husband deserved it, if it was you or not.«
That was enough for Sirius. Powered by pure upsetment and adrenaline he pours his only left over water for that week through the tiny window between him and the screaming one. »Say one more thing about the Potters and I'll make sure to even hunt you down in death«.
This seemed to give the situation the rest. Dementors came storming in, opening the celldoor as he felt, shifting away into unconsciousness multiple times, cold arms wrapping around him and towed him into an extra cell. Sirius never saw it but only knew it from what others told - if they were able to. This was said to be the cell to break even the strongest ones. "Awesome", he thought "As if this night wasn't already terrible enough"
The last thing he saw was a smaller dementors face coming near him, knowing there was only one thing that could happen now...