Severus jumped at the sound of his name, looking up and wishing he'd not been so stupid to let his guard down for even a second. He was just starting to think this place was not totally horrible, as thus far he'd not been molested. But now, he knew who was speaking to him before his eyes registered the face - there were very few voices burned into his memory, and Remus Lupin was one of them.
He instantly reached for his wand, eyes glancing around the room for any concealing corners. Where there was one the others were not far behind, and Severus was not keen on dealing with any of them today.
"Lupin," he hissed, taking in the boy in front of him. He could see that Remus was not in the best of health, a glaring understatement - Remus looked as if he'd got into a fight with an over grown Venomous Tentacula - but Severus couldn't be concerned about the condition of one of his most despised enemies at the moment, he had other things to worry about. "What are you doing here? Where are the rest of them?"