It was clear what was going to happen a moment before it did, but that did not make it any easier to bear, and as Sirius laughed, a high, reckless sound, and as Harry reached for his godfather, far too slow, the world held its breath in readiness.
It all seemed to fade in and out of focus as Sirius toppled back through the veil and vanished forever. Harry was screaming, crying, throwing himself towards the veil with a mad light in his eyes, but then Lupin's arms were locked around him, face grim and tired, holding Harry against his chest.
"Sirius!"
It was like the world was falling apart, and he knew there was nothing he could do, but still he thrashed against Lupin's iron hold, face contorted with fury and anguish. It wasn't supposed to end like this, because this was his godfather, this was Sirius, so alive that sometimes it was painful to behold, and he wasn't supposed to die, not like this.
It felt like there was nothing in Harry's mind save a burning, urgent screaming that he needed Sirius back, needed him back so that Harry could think again, breathe again.
"No! "
It's too late, there's no way out. Sirius is gone, and he's left Harry all alone.