To say he was only slightly mad would have been like calling the Dark Lord only slightly delusional. Severus Snape was livid and enraged, which of course he had wasted no time in letting Minerva know. "Try protecting your little cub now", he had shouted at her before he had taken his leave.
On his way back to the dungeons he had succeeded in taking a further 60 points from Gryffindor, a combined thirty from Ravenclaw and Hufflepuff, and even caught himself taking ten points from his own house after one of the little gits had nearly caused him to change path.
He had never been so angry, not even when it came to Potter and there had been plenty of times when Potter had been the on the receiving end of his murderous rage. Little Miss Know-It-All had succeeded in having an utter breakdown due to the fact that she had finally made a genuine error and Minerva was so willing to look past it. As soon as she had lifted her grubby Gryffindor paw to drop in the dilly flower she had been holding, he had seen his opportunity. She being the little madam that she was, of course, was unable to restrain herself at the possibility of not being so perfect at all. The Lost Child of Ravenclaw had managed to make it through a war semi composed but was unable to process the fact that maybe she didn't know it all after all.
He smirked as he remembered the moment when she had realised what she was doing wrong, all colour had drained from her face and she had promptly progressed into denial and then she had lifted her hand with the ingredient to place it into the cauldron.
Severus Snape suddenly came to an abrupt halt a few yards from his office "and then she had lifted her hand with the ingredient to place it into the cauldron" he muttered. His eyebrows began to rise as he repeated the sentence to himself, louder this time "and then".
Severus did not like where this was going as he began to quickly go over the incident once more. There was no question in his mind now; her reaction had definitely come before she had begun to place the essence of dilly flower into the cauldron. His mind was buzzing with possible scenarios, why would she react first and then act? 'She was acting purposefully' a voice in his head shrieked 'she wanted to cause an accident'.
He could feel his temper rise again as he entered his rooms and began to pour himself a drink. She had wanted to cause a possibly fatal accident, wait until he shoved this in the Headmistress's face. But even as Severus took his first mouthful of whiskey the reasons why this was unlikely began streaming into his head.
Firstly she would rather cut off her own leg than be responsible for endangering Potter and Weasley, and for some unknown reason she was also protective of the rest of the bumbling idiots that belonged to her house. Combined with the fact that she had just fought and survived a callous war and he was certain, had had seen enough casualties to last a lifetime, she simply couldn't have done it purposefully.
Severus began to strain his head for more possible scenarios, replaying the occurrence over and over until he was suddenly very aware of something he had missed. The question wasn't why she had reacted before she had begun to place the ingredients in the cauldron, rather it was, what had caused her sudden reaction?