There is a speck on Sirius's thumb.
He stares at it. The black looks startling against the pale skin, which, in turn, looks startling against the tattered black robes that cover his lap.
His thumb twitches, and he leans closer. Pushes his hair out of his eyes and blinks. There are thin lines running all over his thumb, and the speck is settled perfectly within a groove. He breathes in sharply.
He breathes out.
The little black speck flies off his thumb, wafting through the stale air. His eyes follow it, until it slips through the bars of the window.
He stares at the window for a while. Then lets out another deep breath and goes back to twiddling his thumbs.