A/N – Written for round six of the Quidditch League Fanfiction Competition with the prompt Mystery. I also had the optional prompt 'The Listeners' by Walter de la Mare (which I used very loosely) and Keyhole.
There had always been The Door. It wasn't particularly remarkable – the same as every other interior door in their house, in fact – apart from one small detail. Not once could he remember a time when it had ever been opened.
It wasn't the kind of thing that gnawed on his mind until he had discovered everything about it. For the most part, he could completely forget its existence; it just became another part of the old house. There were other times – few and far between – where it was impossible for him to ignore it.
"What are you doing?"
The obnoxiously loud whisper startled him. He whirled around, heart beating wildly somewhere in the region of his throat.
"Sirius," he hissed, "keep it down!"
"Tell me what you're doing." He didn't even bother attempting to whisper this time.
"Nothing," he couldn't keep the defensive tone out of his voice and that only served to increase his brother's curiosity. What had begun as a half-hearted attempt to gain information which could potentially get his brother in trouble had now become genuine interest.
"C'mon, Regs," Regulus couldn't help a scowl at the dreaded nickname, "just tell me what you're doing and I'll go away."
"No you won't"
"Okay, I probably won't. But I won't tell our parents if you tell me."
Regulus seriously considered the offer for a few seconds, before sighing and shaking his head.
"I'm not doing anything, Sirius." He probably took too long to answer. His brother showed absolutely no signs of leaving.
"'Course you are, otherwise you wouldn't be standing in the hallway acting all suspicious and pretending you weren't doing anything."
"I'm not pretending!"
"The more you deny it, the less I believe you."
"Look, I- Y'know what? Believe what you want. I don't care."
"It'll be quicker just to tell me." Regulus heaved a sigh. It was always difficult dealing with his brother.
"I just thought I heard something, okay. I didn't, so... I'm really not doing anything."
"Oh. That's boring."
"Yeah, well-" Sirius was already turning to leave, and maybe if Regulus had told the truth even five seconds earlier that would have been the end of it.
There was a loud creek, as if someone had stepped on a wonky floorboard or an old staircase. If the house hadn't been so deathly quiet they wouldn't have been able to hear it.
"W-was that you?" Regulus whispered.
"It was probably nothing."
"But-"
"It's an old house. It makes noises. It's nothing."
"But it sounded like it was coming from," Regulus made a vague gesture towards the door; barely moving his hand really, as if that would attract too much attention.
"There's nothing there!"
"Then how come we're not allowed in?"
"We're not allowed in the study, either. Don't see you hanging outside that."
"But that gets used. We know what's in there," at his brother's sceptical look, he adds, "or we can guess, at least. Father's usually in there. This door doesn't even get opened."
"Maybe it's locked."
"What?"
"Well, if it's locked that would explain why it's never opened."
"If it's locked then there must be a key, and why would the person with the key never open the door?"
"Maybe they don't want to."
"Then why bother locking it?" Sirius was clearly growing tired of this.
"You're thinking too much. It's just a door. Why should it matter what's behind it?"
"Because we live here."
"Well, I don't plan on living here any longer than I have to. I honestly don't care what's-"
Sirius was cut off abruptly by a low scraping sound. Regulus briefly entertained the hope that his parents had decided to come home early and move the furniture around. It was like the noise you get when you pull your trunk across the floor rather than picking it up... or the sound of fingernails being slowly dragged across wood.
"Y-yeah, you're r-right. It's pro-probably nothing." He was already moving away from the door, his attempt at sarcasm coming across as denial.
"C'mon, Regs," he didn't even register the name enough to be bothered by it, too focused on trying to get out of the grip Sirius had on his elbow, "you're the one that wanted to know what was behind the door." Sirius gave him That Grin; the one usually reserved for his friends right before he came up with an idea that was almost certain to get them all detention for the rest of the month. It was not a look Regulus particularly wanted aimed at him. "Let's find out."
"No!" His struggles to get away increased.
"Stop being such a baby and-" Sirius gave a particularly hard tug at the exact moment Regulus got his foot caught in the edge of the rug, causing him to stumble forward. He caught himself before he planted face first into the floor, arms bracketed against the door an eyes level with the keyhole.
He was screaming before he could even fully register what it was that he was seeing, making a desperate attempt to scramble away from the door but finding himself unable to move. He was struggling to breath in between screams, his eyes stinging and his chest heaving.
Someone was trying to grab onto his arms and he tried to get away, to curl in on himself, but they were too strong.
He was thrown against the opposite wall, the impact knocking what little breath he had left out of him, and his screams turned into chocked sobs as he stared at the terrified face of his brother.
"What-" Sirius made as if to go and see for himself whatever had caused such a strong reaction in his brother, but Regulus grabbed onto his wrist with a surprisingly strong grip.
"D-don't. Please." Maybe it was the tears still streaming down his face, or the way his hands had begun to shake. Maybe it was the whispered plea. Whatever the reason, Sirius nodded slowly and helped his brother to his feet. He half dragged half carried Regulus down the corridor and away from the door, only looking back once.
Sometimes it was best not to know.