Sirius laughed mirthlessly. "What do you think I am? Mad?"

Not the best question to ask after his display earlier when Remus had just found him. Nor was it good to ask when he had that light in his eye. It belied the dryness of his tone and spoke too clearly of his own mental state. He could feign calmness, cling to what he had of his sanity, but beneath it all his mind crumbled.