What if Alec and Magnus stole some of Isabelle's clothes?
"Alec! Alec!"
Isabelle frowned when she didn't get an answer, storming up to Jace's room. "Jace!" she yelled, banging on the door a few times.
The door opened and Jace appeared, looking as if he had just woken up. "What?" he asked in annoyance, Clary appearing behind him with a yawn. "What could you possibly want?"
"Have you been in my closet?" she accused, crossing her arms with a slight glare.
Jace snorted. "And why the fuck would I want in your closet?" he asked back, leaning against the doorframe. "Unless…" He looked back at Clary then back at Isabelle. "Give us a sec."
"Jace!" Isabelle yelled as the door slammed shut. She tapped her foot in both annoyance and anger as the door opened up again a few minutes later.
"Nope, haven't been in your closet," Jace said, a small grin on his face. "Why don't you check with Alec?"
"And why would he—" Isabelle stopped short, realizing what happened. "He is so dead."
"10 bucks and a seraph blade Alec took whatever Izzy's missing and is using it right now with Magnus," Clary bet, grinning up at Jace.
The blonde grinned back, closing the door. "I'll take that bet," he agreed.
"Stupid…" Isabelle mumbled, storming her way down the street to where Magnus was staying, "…idiotic…fucking…brother…and his…fucking…warlock…boyfriend. Stealing…the leather outfit…that I was going to use with Simon…He…is…so…dead." She came up to the front door and instead of knocking politely like the lady she was, promptly broke it down like the Shadowhunter she was.
Alec opened his eyes, hearing something from downstairs. "Magnus," he moaned softly, the warlock stopping in his ministrations. "Did you hear something?"
"Just you, my little Nephilim," the warlock crooned, a grin on his face. He ran his hands down Alec's torso, resting on his leather-clad hips. "Where did you get this outfit, by the way?" His grin grew slightly. "It looks like something your sister would wear with her little vampire boyfriend."
Alec was currently under his boyfriend in a black leather miniskirt that clung to his hips and barely covered anything, a pair of black leather thigh-high stiletto boots, and a black leather corset that hugged his chest and stopped just above his stomach.
"Shit," Alec cursed, hearing stomping grow closer. "Magnus, get us out of here."
"Why should I do that?" the warlock asked. "This might be fun to watch."
"Because she'll kill me for taking this and because…" Alec leaned up, whispering something in his boyfriend's ear.
Magnus' eyes widened, a sly grin gracing his features. "Of course, my angel," he whispered, snapping.
"Alec!" Isabelle yelled, slamming the door open just to see the two disappear in a poof of glitter. "Alec Lightwood!" she screamed, hands clenching at her sides. "When you get your Shadowhunter ass back here, I'm going to tear you apart!"
Meanwhile, in another part of the world, a certain warlock was busy stripping a certain Shadowhunter of his very sexy outfit.