Disclaimer: I don't own anything. I just came up with the crazy concept that is this piece of rambling.
A/N: sorry for the randomness. Hope you enjoy it!
Horace Slughorn considered himself something of a detective. He liked to think that if there was anything going on under the surface at Hogwarts, he would find out about it. And so it was that he discovered something quite unusual while snooping around Severus Snape's office late one Wednesday night.
Ducking his head into each room with an 'open' (not locked and sealed magically) door, Horace was quite surprised to hear low voices coming from behind the door that lead to Snape's office. He put his ear to the door and could hear snatches of a conversation which was between Severus (obviously), and someone who sounded familiar but whose voice he couldn't quite place…
'Please, you know I can't…'
'…not an optional extra, you know…'
'If you don't do this, I refuse to buy you a Christmas present this year.'
'It's not like you've bought me one before.'
'... shut up and do it, or I'll…'
'That's IT! I'm outta here. Let me know when you're ready to treat me like an equal.'
Heavy, stomping footsteps approached the door.
'You're not… you're my-'
But at that point the door opened, and Horace barely had time to rearrange himself so that he looked like he was about to knock, before Harry Potter wrenched the door open and barrelled into him.
"Professor!" he exclaimed, "I'm sorry, I- what are you doing here?"
"Potter!" Snape growled, "Professor Slughorn is a teacher. You should show him a little more respect." Horace thought he caught a mumble on the end that sounded something like 'more than you show me, anyway'.
Harry had the decency to blush, though Horace was unsure as to whether it was the audible comment or the mumble which had caused his embarrassment.
"Sorry, Professor Slughorn. I'll just – see you in potions tomorrow!" He gushed, and took off in the direction of the stairs.
"Horace," Snape said silkily. Horace gulped. "What are you doing here?"
"It was just –" Horace began, thinking quickly. "I was just wondering, Severus, if you could knock me up a Pepper Up potion."
"Surely you could do that yourself, Horace. You are, after all, the Potions Professor at this school," Snape said, beginning to look almost – amused.
"Well, under normal circumstances, of course," Horace mumbled, "but you see, Severus, I'm feeling a bit – stuffy – in the head, you know how it gets, and I'm not sure I ought to be trying to make any type of potion with my brain feeling this fuggy."
"Fuggy brain, you say?" Severus said, sounding highly amused and trying to keep the smile off his face. "Well, let me see, Horace. Just a moment"
Severus disappeared and returned a moment later with a Pepper Up potion. "You'll want to drink that right away, Horace, before you continue your night time stroll," Severus commented.
"Why – yes, of course," Horace said, feeling a little apprehensive as, Potions Master or no, he had no idea what the effect might be of drinking a Pepper Up potion unnecessarily might be. He sighed lightly, and downed the potion.
"Phew. Dat's bedder. Danks, Severus," Horace wheezed, feeling as though he may now have actually developed a fuggy brain.
Severus smiled politely. "You're very welcome, Horace. Good night," he replied, closing the door in Horace's face.
Well, Horace thought, making his way clumsily up to the hospital wing to see Madam Pomfrey for another Pepper Up potion. It seemed they worked as toggles on and off between fuggy and non-fuggy head. That was interesting. I wonder what they were doing together. Horace resolved to find out more, starting in Potions the next day.
However, by the time his class with Harry had rolled around, Horace had many more important things on his mind than finding out the extent of the 'student-teacher' relationship between two people whom, until recently, Horace had believed hated each other.
Luckily for Horace, two clues unfolded right in front of his eyes (and perked up ears) in his class that day.
"Harry, where were you last night? I was asleep by the time you got in!" Ron was saying as Horace walked past their cauldron for the first of what was to be many, many times that afternoon.
"I had a lesson with Snape, remember?" Harry said distractedly, glancing at his potions book before picking up his silver dagger.
"But I thought your lessons were on Mondays."
"But… yesterday was Wednesday."
For a moment, Harry looked mildly distressed, but this went unnoticed by all except Horace.
Then – "I had to have an extra."
"Sucks to be you mate," Ron said emphatically.
"Yep." Harry said, carefully crushing his Sopophorous Bean with the flat side of his dagger rather than cutting it.
Horace watched Harry interestedly, remembering that another of his students, years ago, had used the same technique to great effect. He was astonished, however, when he saw Harry adding a clockwise stir after every seventh counter-clockwise stir. The resemblance between Harry's potion-making style and Severus Snape's was incredible.
At the end of the class, Harry's potion was – as expected – perfect, but his was the only one. The Draught of Living Death was apparently too difficult for most of the students to accomplish.
Horace recalled that Harry's mother had been excellent at potions, too, but the similarities between Harry and Severus were too strong for him to ignore. He knew he had come to a likely conclusion, and decided to snoop again tonight to hopefully prove his theory.
When he arrived at the door to Snape's office that night, he could hear voices again.
"I can't do it, it's too hard," a voice that Horace now recognised as Harry's sounded very distressed.
"Shh, I know, Harry, it's okay. We can try again tomorrow."
"OHO!" Horace burst out, pushing the door open to reveal a sobbing Harry wrapped in Severus' arms. The pair sprang apart immediately, but Horace merely grinned at them.
"I've worked out your little secret!" Horace said, gleefully.
"You have, have you, Horace?" Severus said evenly, clearly inviting Horace to tell them what he thought he had discovered.
Harry looked worried. Horace smiled again, and said "I've worked it out. Merlin knows how this came about, but I've never been surer in my life. Severus, you're Harry's real father, aren't you?" Horace said, looking smug and clearly not expecting an answer.
Severus and Harry looked stunned for a moment, and then Harry burst out "what gave you that idea?"
"Why, Harry, I should think it's obvious. You've clearly inherited his talent for potions."
"My -?" Severus started, finding himself unable to comprehend the situation, let alone finish his question.
"Yes, your talent for potions. I saw him make a perfect Draught of Living Death this afternoon, and guess what he did? He crushed his Sopophorus Bean with the flat side of his dagger and added a clockwise turn after every seventh stir counter-clockwise. It's just what you used to do in school, Severus. You remember."
"Indeed I do," Severus said. "Now, Horace, I wonder if you would let us return to our – private – conversation?"
"Oh, family matters. Of course. I see." And without another word, Horace left, whistling happily to himself.
Back in Severus' office, Harry gulped and looked at his professor nervously.
"You know, Sev, I won a bottle of-"
"My book, Potter?!" Severus yelled. "You have my old potions book?"
"Uh… I guess so, if it's true that you used to do that stuff."
"Have you read it yet?"
"Uh – no," Harry said, looking confused.
"You will fetch it for me. Now."
"But, Sev, it helped me in class today – you know you're really good at-"
Harry yelped, and ran up to Gryffindor Tower.
He was back just 5 minutes later, panting to catch his breath, and held the book out to his Defense Against the Dark Arts Professor.
"I never want you to look in this book again. Never."
"There are Dark spells in this book, Harry."
"You wrote them in there? Why would you have done that?"
"You know how I was back then."
"So… what if I promise not to try any of the spells?"
"I'll help you with your potions, if you are really struggling that much."
"That's okay, Harry."
Severus held his arms out and Harry moved into them for an embrace.
Sighing contentedly with his head leaning against the taller man's chest, Harry suddenly snorted with laughter.
"What is it?"
"I can't believe he thought I was your son."
"I know, that was a very odd conclusion – in fact, the most illogical one he could have come to, really. He seemed to know about our meetings, why didn't he assume I was tutoring you in potions?" Severus mused.
"Hum. Well he did see us like this. Do you think he'll tell anyone?"
"No, Horace likes to work out secrets but he feels like his work was in vain if everyone knows. He'll keep it to himself. We should be more careful, though."
"Yeah," Harry agreed, standing on his toes to press a chaste kiss to his lover's mouth. "Lucky he didn't catch us doing this," he murmured, drawing Severus into a more passionate kiss.
"OHO!" Came a shout from the door.
Harry and Severus groaned in unison.