Harry potter fic….

Once upon a time, there was a fic on ffn, where shit happened and the Slytherin/gryffindore potions class got trapped in the classroom for two or three weeks? A while, at least. And harry was abused and was already starving and beaten, etc. And snape was like ???? Protect the young bean. Tried looking for it a bit ago, and every few months I got, I wanna read that fic. So if anyone has a link to it, or has it downloaded, help a potterhead out?