For SiriusMarauderFan's Father's Day Challenge:

Septimus looked over with a smile at Arthus, who was cuddling in the corner with all the model airplanes they had bought him for Christmas.

"How do they work," he had asked, awe shimmering in his eyes as he looked up innocently at his father.

"I don't know, son." Semptimus had told him, and smiled. "All I can think of is that the muggles have some sort of…er, muggle levitation charm on it."

"But they fly so high," Arthur would protested. "I can barely levitate a feather five feet into the air."

Septimus had given him a hearty laugh. "Billius can levitate things a bit higher." He had told his youngest son, referring to Arthur's older brother. Arthur had just rolled his eyes again and began fiddling with the airplanes. Just by the look on his face, Septimus could tell that his son was considering taking all its pieces apart to see how it worked, although Cedrella had warned him that this little entertaining piece of plastic was not a real model, but just an outside structure for muggles to play with. Arthur was still ecstatic about his gift, though maybe slightly put out.

Despite his overexcitement at attending Hogwarts, Arthur was still interested in the Muggle-world. He had been ever since they had taken Billius to the platform for his first year. Arthur was flabbergasted by the sheer strangeness of muggle inventions, and he wouldn't keep quiet about it until they got home. Cedrella and Septimus, were, of course, very supportive of Arthur's accepting nature and his unbiased thoughts toward muggles, but Septimus could not help but be worried at times.

They were living in hard times- times of You-Know-Who standing at the height of his power. Their era did not call for Muggle-supporters. Cedrella and Septimus, of course, had nothing at all against the non-magical folk and would readily fight for their rights. But their children…

Billius was highly interested in divination, though personally Septimus thought it was all a load of dung. But despite the many interests Hogwarts provided, Arthur refused to let go of his love for muggle inventions. He had sworn to every deity he could think of, that he would take Muggle Studies once he entered his third year.

Septimus did not have the heart to tell his son the danger this simple passion could bring him. The Weasleys were already under negative light- Cedrella, a former Black, was considered a blood traitor now that she had married a Weasley, also a blood traitor. Both of them did not wish to discourage Arthur of his future intentions and day dreams which no doubt included finding out how airplanes stayed afloat, but as any reasonable parent would have been, they were concerned.

Which was why Septimus was now mulling over his thoughts, watching his son, who was currently examining his planes closer, adjusting his glasses and squinting his blue eyes.

Should he warn Arthur? Tell him to keep his compassion for Muggles a secret? But didn't that make Septimus hypocritical, like all those haughty purebloods? He wasn't ashamed of Arthur and his determination to understand the muggles, nor did he wish to discourage his son, but if anything happened to Arthur, he would never forgive himself for not advising his son, and neither would Cedrella.

But..would his little boy be able to understand? Would his innocent mind be accepting of the true magnitude his small hobby would leave, of how much of target he'd become in You-Know-Who's ranks?
Why, only last month, the Muggle Studies teacher had been killed! And thirteen Muggle-Borns with her.

Septimus closed his eyes, trying to think of what Cedrella would say in this situation.

Calm down, dear, she'd sooth. Let Arthur have his way for a little while. You can talk to him if you want, but he's a stubborn as a hippogriff, that one.

Septimus sighed, wishing Cedrella really was here and not out. She could keep her head leveled out in this situation. She was the harsh, tough one who wasn't afraid to drag Billius by his ear when he came home with a smuggled niffler hidden in his trunk. Septimus was the kind of man who would laugh at Billius and pat his shoulder in sympathy.

He, at first, thought this shouldn't worry him, as he himself had had several interests he had let go of by passing time. But it had been three solid years, and Arthur was a attached to Muggles as strongly as he was when he first got interested in them.

Septimus hesitated for a moment, thoughts and ideal ways to start the conversation rushing through his desperate mind.

He opened his mouth, closed it, and then opened it again, but Arthur took no notice of this as he happily flicked through the pages of a book about something- most likely other muggle inventions- and occasionally looking fondly at him planes.

Decided to start at the beginning, Septimus opened his mouth, only to have Arthur beat him to it.

"Dad?" Arthur said excitedly, his eyes lighting up like they always did when the gears of his brain were turning.

"Um, yes, son?" Septimus asked, not knowing whether to be irritated because it would take quite some time to recollect the courage he'd picked up and try to bring up the dreaded conversation, or relived because he had avoided it this time altogether. He took a deep breath, and held it. He had to do this. "I want to talk to you after this, in any case." An even more enormous relief washed over Septimus as he uttered these words, as if a burden had been lifted off his shoulders. Arthur looked at his father worriedly, but did not detect any sign of anger, so he assumed he was not in trouble. Cheerfully, still, Arthur continued.

"Dad, did you know that airplanes were first invented by two brothers called the Wrights?" he demanded.

"No, as a matter of fact, Arthur." Septimus said. "I didn't."

"Well, now you do." Arthur said, picking up the book and a model airplane before prancing to his father and making himself comfortable in his lap. That was another thing Septimus loved about his son- unlike Billius, Arthur was not ashamed to show affection to his parents whatsoever.

"Look, dad." Arthur said, pointing at a paragraph. "They tried again and again to construct a plane, and people mocked them and didn't believe they could do it, dad, but they did! And it's really thanks to them that Muggles can travel long distances, too. I want to just like them when I grow up, dad! "

Septimus' eyes darted across the words and he saw that his son of right. He held his breath. Arthur looked up concernedly, worried he was in trouble after all.

"What did you want to talk to me about, though?" Arthur asked.

Septimus looked at his son. And at that very moment, the words he wanted to say vaporized. He didn't know why, or how, but somehow, it all became unnecessary in that brief moment. Arthur was just a small, bespectacled eleven year-old boy, and yet he was so much more. In him, Septimus could clearly see the man his son would grow to be. One who would grow up to fight for what he thought was right. In his sparkling blue eyes Septimus could see just how much that one paragraph could show him through clear vision just what was in front of them. He would, indeed, never let anyone else's opinion get in the way of what he loved, and his parents were no exception. And suddenly, Septimus felt as though there was really no use for his worries.

"Someday, Arthur," Septimus promised. "you're going to be a great, great man."

Arthur beamed with happiness and hugged his father around the middle, not knowing just how true that sentence was.