It was a cold and late January evening. The dungeons were the darkest and most unwelcoming at this time of the year. The only thing which kept the potions master of Hogwarts warm was the enormous fire in his fireplace. It had to burn day and night to keep his quarters sort of comfortable. Said potions master was poking the fire and warming his hands. He sighed and sat down in the only chair nearby the warmth of the fire. There wasn't much other light in the room, but the soft light of the flames didn't mask the troubled look on the face of Severus Snape.

His thoughts went back to the events of that day. It hadn't seemed an abnormal day until later in the afternoon. His colleague and bane of his existence Harry bloody Potter had asked him to overlook his lesson for that day. Once a week an older member of the staff had to supervise the members who had just started the job. It was a new policy of the Headmistress, and in Severus' opinion a good one. The older professors could help the younger ones by giving advice and helping them with some harder theories.

All the other professors must have been busy, otherwise Potter would surely have chosen another. It was just after his last class for that day. The students had just left when there had been a knock on his door. One of those thunderheads must have forgotten their books…

"What?" He shouted without looking up from his desk.

"Professor Snape, I'm sorry if I'm interrupting you?" He heard a lot lower voice ask than he suspected.

He looked up to see Potter standing there. He… had aged. That was one thing for sure. He wasn't the awkward schoolboy anymore. He had seen too much for that, lost too many friends and fought too hard.

"Professor Potter" Severus sneered, "what can I help you with?"

Potter looked tired at the misuse of his title but didn't comment on it. "I was wondering if you could attend my last class of today. The seventh years, Gryffindor and Slytherin."

Severus raised his eyebrow at this. "I expect you would have asked anyone else if there was someone available."

Potter looked like he was about to protest but Severus cut him off. "But very well. I will supervise your class. But do not expect any help whatsoever, Potter. I am sure that my other foolish colleagues practically gave your lesson for you, but I am not so easily persuaded."

Potter's face became a little red at this. Severus couldn't help but smirk evilly. But to his disappointment Potter just took a deep breath and said calmly, "So very nice of you, professor. I'll see you in ten minutes in the Defense Against the Dark Arts classroom." Abruptly Potter turned around and marched out of the cold potions classroom.

Severus arrived ten minutes later as promised in the classroom. Potter was already there. Without saying a thing, Severus sat down in a corner of the room and took out his notebook. Than to his astonishment, Potter walked to the door of the room and waited for his students to come in, one by one and he greeted them all personally. Most of them received a firm handshake. Others received that, and a small talk about a former assignment, or just about how their day had been.

When everyone had taken their seats Potter started his lesson.

"Good afternoon everyone. As you all can see we have a guest today. He is here to observe and nothing else. Please just behave like you would normally do without Professor Snape here."

Severus hadn't expected that. He thought Potter would have asked the children to be on their best behavior, but nothing of that sort. Potter than calmly continued his lesson. First he explained the theory and answered some questions. Then he divided the students in pairs of two and the practical part of the lesson began. But instead of just standing in front of the classroom, Potter walked through his room and answered questions of every pair.

Than something happened that Severus expected to happen. A Gryffindor hexed a Slytherin on purpose. Severus thought that Potter would ignore this or give blame to the Slytherin. Instead, Potter actually took points from the Gryffindor and even gave him detention.

Severus was impressed. Not only did Potter have excellent teaching skills, he seemed to own the room like it was his territory. Not one student spoke out of term, not one incident and not once did Severus have to intervene. When the lesson ended Potter stood again at the door of the room and greeted everyone on their way out. It was friendly but formal. When the last student had left the room Potter turned to Severus.

"I always greet all my students. It gives me a good idea of their mood and the atmosphere in a class. They aren't just students you know. They are their own person. And they like it when you really see them as a person." Potter sat down upon one of the desks and was silent for a while. Then he frowned. "Well? Aren't you going to tell me what a bad job I've done?"

Severus swallowed. He couldn't for the life of him lie about this, Potter had done an amazing job. He had authority, was friendly to his students, knew his materials and could keep order in the classroom almost as good as Severus did. Only Potter did this without making students fear him like he was Satan himself.

"You.. did well actually. I will report this to the Headmistress." He said all of this in an uncharacteristically soft voice. And stood up to leave, but Potter stopped him.

"So you are telling me that you think I did good?" Potter said unbelievingly.

Severus regained some of himself, "It was not a total disaster, yes."

With that he left the room, leaving a stunned Harry Potter in his absence.

Now Severus Snape stared at his fireplace. Potter shocked him to his core today. He honestly believed that the boy couldn't teach and that hiring him had been a big mistake. It seemed that he had been wrong. About what else had he been wrong?