"I don't have to tell you anything," Severus all but hissed in indignation. He lowered his voice and looked about to make sure that no one was eavesdropping before forcing himself to lean closer again.
"You can't possibly learn what I know; don't make me laugh, Lupin. It's too complex and I don't fancy myself a very good teacher." Eyes narrowed and he spat the next:
"If he doesn't want to find a solution, then tell him to rot in Hades for all I care."