Expecting someone else (слэш)

Severus knows that James Potter's son is coming to Hogwarts. He has many expectations-a brash, idiotic boy who was proud. He isn't expecting a shy boy who flinches from everyone-even as he takes everything in with a look of wonder. And the flinching causes a deep, growing fear in Severus.
Having abused children at Hogwarts is not a new thing. But it never gets easier when you recognize the signs. And he can't help but to notice them in his Best Friends-Lily's, son.
Sounds super angsty, but it's a one shot with fluff at the end!