For Telturwen, as part of the September Oneshot Exchange.

It happens in a flash.

His foot catches, and his heart squeezes in his chest. This is how he's going to go- fallen to his death in a broken heap at the bottom of the still moving staircase.

"Careful!"

He's pulled back by a strength that does not match the the slender fingers curled around his shoulder. "I, um, thanks," Regulus mumbles, his cheeks burning red.

Evan Rosier offers him a crooked grin. "How often does someone like me get to play the knight in shining armor?" he laughs, and Regulus is all too aware that Evan is still touching him.

"I'd better go," Regulus mumbles.

"See you around."

…

He sits in the library, teeth worrying against the nail of his thumb. His eyes move over the pages of the book, but he doesn't quite see the words.

Evan is still on his mind. An hour later, and he can still feel where the older boy's hand had been.

"You're being ridiculous," he tells himself, earning a look of disapproval from Madam Pince.

Regulus slams the book shut, pushing it aside before rising to his feet and quickly rushing from the library.

…

"Black!" Evan calls as Regulus enters the common room. "Come join me for a game of chess."

"I'm actually not very good at it," Regulus admits, but he's drawn to the table as though he has no control over his movements.

"Surely you know how to play, at least."

"My brother taught me when I was younger."

"So, the traitor is good for something."

Regulus stares, indignant. Even if he and Sirius aren't particularly close anymore, even if there's more bad blood than good between them now, he still can't stand to hear anyone say a word against his older brother.

"Seems I've struck a nerve," Evan says, and his smirk tells Regulus that he had meant to. "Sit. I'd love to play you."

Regulus sits across from him, staring at the pieces.

"The important thing is to think ahead," Evan instructs, making his first move. "Don't just focus on what's a good move now. Strategy is key."

"Should you really give advice to your opponent?"

"What can I say?" Evan laughs, leaning back lazily in his chair, a grin tugging at his lips. "I like you enough to not see you suffer."

"I'll keep that in mind," Regulus says as his pawn moves forward.

…

"A little birdie has told me that Evan Rosier has taken a liking to you."

Regulus turns, scowling at his brother. "And what's it to you?" he asks, folding his arms over his chest. "You left, remember? You don't get much say in who I allow in my life."

Sirius raises his brows. "Allow in your life?" he repeats. "Sounds like you're getting pretty friendly."

Regulus groans. He doesn't want to hear it, especially not from Sirius. Sirius has abandoned him. Sirius has left him to deal with their parents' constant fighting. He has no right to swoop in now and try to be a big brother.

"I'm not telling you what to do, okay?" Sirius says, his voice softening. "I just think it would be wise to be careful around Rosier. He's dangerous."

"Dangerous?"

There's an almost pained expression on his older brother's face. Just a flicker of something warring inside of him. "He's close to Bellatrix. He shares her views," Sirius says. "There's talk that she is trying to recruit him."

Regulus shakes his head. "Are you trying to make me hate you?"

"Is it working?" Sirius asks jokingly. "No. I'm trying to look out for you."

"By interfering in my relationships?"

"Rela- Regulus, no. I get it. He's older. He's smart and fierce. You're young and impressionable. But Evan Rosier will lead you down a dangerous road, and I'm not sure that I will be able to bring you back from it."

"Yeah? Well, who asked you to?" Regulus demands. "You think you can just run away and expect me to welcome you with open arms whenever you decide it's convenient to care about me?"

"I always care about you. I'm-"

"You can shove your apologies up your arse. Excuse me. I have things to do."

…

"You're late," Evan says, smirking. "And here I thought you'd stood me up."

Regulus feels color stain his cheeks. "I wouldn't," he mumbles.

"Good. Time for a swim, then."

"I didn't bring any swimming clothes."

Another smirk, more wicked now. Regulus shivers in spite of the warm breeze. "You don't need clothes to swim," he says, trailing a finger down Regulus' chest, pausing at the bottom of his shirt. "In fact, I'd much rather you didn't wear any."

"If anyone sees-"

"No one will. No one ever comes out this late," Evan assures him, and Regulus is drawn in by that velvet voice.

Suddenly, he thinks that he would follow Evan to the end of the earth. He'd do anything for him.

He's dangerous.

But Regulus doesn't care. He pulls his shirt away, tossing it carelessly to the side.

…

They sit by the fire, both still wet and shivering.

"How does it feel?" Evan asks.

"What?"

"To live a little?"

Regulus grins. "Amazing."

…

They steal kisses in the empty classroom. Regulus knows that they could be caught, but he can't bring himself to care.

"God, you're so good," Evan murmurs.

Regulus smiles into the kiss.

…

He's dangerous.

Sirius' warning echoes in his head as he tries to fall asleep.

Regulus wonders if it's true. The older boy has a hold on him, one that Regulus can't quite explain. It's dangerous, maybe even foolish, to allow someone to have that effect on him.

But he can't resist the temptation. Dangerous or not, he wants Evan. He will take whatever risks he has to as long as it means being with him.

He's dangerous.

But Regulus doesn't think that he minds the danger.

…

"Where are we going?" Regulus asks.

"Trust me."

And Regulus does, so completely that it almost scares him. He doesn't question Evan further as the older boy leads him across the ground to the Forbidden Forest.

A familiar face appears through the trees.

"Bel-"

But Evan claps his hand firmly over Regulus' mouth. "Dammit, Reg," he groans. "You can't draw attention to her. She isn't even supposed to be here."

Regulus nods, and Evan drops his hand, guiding him into the forest.

"Regulus," Bellatrix says, smiling. "My sweet cousin. I was beginning to worry you might end up like your brother."

"Obviously I haven't."

"Obviously," she agrees before turning to Evan. "Did you tell him anything?"

"Too many eager ears at Hogwarts," Evan says, making a face. "I figured it would be best to wait."

"Tell me what?"

"I've made my decision," Evan says. "I've joining the Dark Lord when I leave Hogwarts."

Regulus feels his heart sink to his stomach.

He's dangerous.

Sirius had told him that they'd expected it. But Regulus hadn't quite believed him.

"Oh."

"You could join me," Evan continues.

"When I found out he was getting so close to you, I had to pounce on the opportunity. Sirius is a traitor. Andromeda is a traitor. Narcissa prefers to play it safe and let her husband take the risks," Bellatrix says, leaning against a tree, offering her cousin a wicked grin. "I'm the only Black willing to do what needs to be done to preserve our family's values. But I don't have to be. You can join me. Join us."

His head feels like it's spinning. Regulus grips Evan tightly for support as he tries to take it all in. "I don't- I mean, I haven't even- I-"

"Reg," Evan says, holding him gently. "Think about what it would mean for us. We would be together, side by side, fighting for the same cause. I want that. I want you with me in everything that I do."

Regulus swallows dryly.

"I know you have it in you, little cousin," Bellatrix says in a voice that's far too sweet for her. "You want to make your family proud. Bring back the honor that Sirius has stolen."

"Join me," Evan whispers, kissing the corner of Regulus' mouth.

And everything within him says no. It tells him to turn and run away, to never even think of Evan again.

But his touch, his kiss, his velvet words. Regulus feels himself pulled in, and he knows that he is trapped.

And somehow, he doesn't mind.

"Okay," he says quietly.

…

The Dark Mark burns into his skin. Regulus throws his head back, clenching his jaw until it stings, trying not to scream.

A gentle hand rests on his shoulder. "I knew you'd want this," Evan says proudly. "You know it's best for us."

Regulus gives a weak smile.

Evan Rosier will lead you down a dangerous road.

Regulus realizes now that it's true. And yet, as Evan pulls him out of the room, his lips heavy on Regulus', Regulus can't bring himself to care.