Severus didn't reply to the words at first, he just looked at the other man, letting their gazes link in some sort of understanding or agreement. Funny how they can actually deal with each other considering they are part of two opposite area of the same spectrum. Lupin was a dark creature true, but he was the apotheosis of good, he would do everything for his friends and for others, a true gryffindor. He on the other hand... he was evil... they were supposed to have nothing to do with each other.
"Thanks are for people very different from me, Lupin." he said then, his eyes slowly darkening, closing off, going back to hide his soul completely. He stepped back with a nod of greeting, and slowly he closed the door.
Sighing, he went back to his desk, looking at the ingredients on the potion magazine's listings. He was glad Lupin hadn't mentioned how incoherent he was being with accepting to help him.