Sirius hangs there in midair for a few moments. He's always worn his emotions on his sleeve - no Black made a good Occlumens, save perhaps Narcissa, and of the Marauders Sirius had always been the absolute worst at hiding his thoughts - but his current expression is hard to read. Not because he is trying to obscure his reaction, but because there are too many things to react to. Gradually, clearer feelings unwind themselves from the knot in his chest and play across his face.

Shock. Disbelief. Dawning understanding. Horror.

Sirius Black sits on his broom and stares at Severus Snape, and for once the disgust on his face isn't aimed at the Slytherin. It didn't take a brilliant Legilimens to understand why: no one had told him. So many of his friends here were from future points in his world, and none of them had seen fit to tell Sirius his fate.

"You're lying. You'd...say anything." Oh such a broken note in his voice, but being broken in the face of overwhelming emotion was not a good sign. Sirius had not yet gotten around to feeling anger, but Snape of all people should know that it's coming. When the storm of Sirius's pain breaks, it would need an outlet, and Snape was his very favorite scapegoat.

This could get very ugly.