When Sirius flung himself into a broom closet to hide from Filch, it hadn’t occurred to him that it might be occupied. It certainly hadn’t occurred to him that it might be occupied by Remus and Mary MacDonald.
Sirius spun to face the door and shut his eyes tight, “Sorry!” He whispered, hearing Filch in the corridor outside the door. “I didn’t know—” Was Mary giggling? Wait. Was Remus giggling? He turned to look at them warily and found them leaning against the back wall of the closet barely stifling their laughter. One look at Sirius’ face and Mary had to cover her mouth to stop the laughter.
Remus was chewing on his bottom lip, looking anywhere but at Mary or Sirius and his shoulders were shaking violently. Sirius noticed how thoroughly kissed his lips looked and the lines Mary's fingers had dragged through his hair and turned back to face the door. But that just made the giggling worse.
“Muffliato,” Sirius whispered and felt the familiar cocoon of the silencing spell and turned back to them. “The fuck is wrong with the pair of you?”
Remus and Mary made tentative eye contact before Mary let out an almighty snort and then they were off again. Sirius didn’t remember the last time he’d seen Remus laugh this hard. He felt very much like he was intruding.
“As soon as Filch is gone, I’ll go.” He said with a frown. “And you can go back to… whatever it was you were doing in here.”
“Remus was just talking about you, actually,” Mary said, between gasps for air.
“Shut the fuck up.” Remus shook his head and covered his face. “Sorry, Pads. We weren’t expecting company.”
“One rarely does in a broom closet Moony,” Sirius said tightly, and somehow that set Mary off again. “You smoked?” Remus smiled at him, one side of his mouth lifting higher than the other in that perfectly Moony way, and he immediately knew the answer to that question. “Right.”
“You were in detention.” Remus shrugged, “Didn’t know I needed your permission.”
Mary whispered something into Remus’ ear that made him flush crimson and then she had to lean on the wall because she was laughing so hard.
Sirius didn’t want to snap, but it felt like they were talking about him behind his back, in front of his face, and he didn’t like that at all. “I’ve obviously missed something.” He pressed his ear to the door, hearing nothing. “I’m going to—”
“No, you stay Sirius!” Mary stepped towards the door. “Filch isn’t looking for me, I’ll grab a cloth or something and if the coast is clear I’ll let you know.”
This felt suspicious, but Sirius nodded. When Mary poked her head out and then left the broom cupboard, she slammed the door behind her and they both heard it lock.
“Mary!” Remus called after her, before covering his mouth and staring at the corner of the room trying not to laugh.
“Since when do you and MacDonald smoke together?” Sirius leant back against the door and crossed his arms.
“Jealous?”
It wasn’t the response that Sirius was expecting, especially as he realised that he actually was jealous. “Didn’t know you liked her, that’s all.”
“Ah, no. Not like that.” Remus smiled again and Sirius wanted to shake him.
“I just walked in on the two of you kissing in a broom cupboard.” Sirius was unimpressed at how this entire evening had gone.
“And you’ve never kissed someone you’re not into in a broom closet?”
“Yeah, but I’m not you.” Sirius studied him. “So what’s going on if you’re not into her like that?”
“We wanted to test something.” Remus’ mouth twitched. “For science.”
Sirius frowned, “The fuck are you on about?”
“Recently, Mary has had feelings for someone, and she wanted to know what it meant. I’ve been going through something similar. It made sense to… you know, with someone we trust, and aren’t interested in.”
“Yeah, still none the wiser.”
“I wanted to know if I was still attracted to girls,” Remus said plainly. “Mary, the opposite.”
Sirius just blinked at him. “You think you like boys?
“No,” Remus’ smile dropped, “I know I like boys. I wanted to see if I still like girls too.”
Sirius’ brain malfunctioned. “You know?”
Remus laughed softly, “Yes. I know. Why? You offering to test that hypothesis if I wasn’t sure?” It was the wrong thing to say, Remus realised, as Sirius had gone very still, and was focused on the only broom in the inadequately stocked broom closet. “Pads, I’m joking.”
“So, are you into girls as well?” He asked quietly.
Remus nodded, “All signs point that way.”
“I don’t think I am.” It was barely a whisper and it took Remus a few seconds to digest this new information. “I don’t think I ever have been.”
“Oh.” Remus wasn’t laughing anymore. “How do you know?”
Sirius arched an aristocratic eyebrow. “How do you think?”
“Right, yeah.” Remus’ mouth was suddenly dry.
“So when Mary said you’d just been talking about me?” Sirius stepped away from the door, closer to Remus.
“She wanted to know how I realised I was attracted to boys,” Remus said, worrying his bottom lip between his teeth. “So I told her about the time you fell on me when you tried to climb that tree by the lake.”
Sirius stared at him, “That was your gay awakening?”
“Bi, but yes. I don’t know if you’ve ever had your hot best friend literally fall from the sky into your lap, but that’ll do it apparently. Now you understand the giggling when you showed up, and Mary locking us in.”
Any signs of uncertainty vanished from Sirius as he grinned. “You know… falling into your hot best friends lap has similar effects.”