This is one of my personal favorites. Enjoy.
It's late, and somewhere in the castle Sirius hears the deep toll of a clock counting out the hours. All he knows is that it's dark, and cold, and the moonlight is flowing strong and bright through the window of his dormitory. It's reflecting off of the mirror he's holding in his hand, and for a moment he plays with the light, scattering it around the room before Remus's face appears in the glass.
"Sirius?" he whispers.
"Here," he responds, and forces his eyes into blankness and his mouth into a small smile as he takes in Remus's injuries. He hasn't found anything yet that stops the twisting of his stomach or the irregular beat of his heart, and it hurts, every time. He'd seen some of the cuts and bruises this morning, after the change, but Pomfrey had been early and they had had to escape before their usual inspection to avoid being caught.
He knew that everything looked worse in the dark, but the deep purple and slashing red that had taken over Remus's face were painful reminders of what he had just been through.
"You're not supposed to smoke," Remus scolds him, voice rough.
Sirius just shrugs, flicking some of the drooping ash out the window, because he knows he isn't.
"You're supposed to be resting," he counters.
Remus shuffles away from the mirror a little bit, tucking his head down. "You said to call you if I needed anything."
He had, the very first night he'd given Remus one of his two-way mirrors. Ever since then, Sirius has waited with the mirror in his hand every night after the full moon. Sometimes Remus uses the mirror, sometimes not. He always waits.
Sirius takes another drag from his cigarette, wondering what Remus could possibly need this time of night. "And?"
"I need you."
Sirius feels his heart stutter, a warm blush moving across his cheeks. He takes a moment to respond. "What's wrong?"
Remus shakes his head, a barely discernible motion in the dimness of the Hospital Wing. "I just need you."
Something warm and messy and familiar twists in his chest, a feeling Sirius has come to call loving Remus Lupin.
He stares back into dark amber eyes, sees the unspoken vulnerability. "I'll be there."
In a moment he is, body tucked away beneath James's invisibility cloak and standing in front of the usual bed, with Remus looking at him in a way that's making it difficult for him to breathe.
"I had a nightmare," Remus whispers, and he sounds lost. "I just needed to know-"
Sirius puts his hands in Remus's hair, has to touch him, has to let him know that whatever demons had entered his head, he was there, and he was real, and he was not letting Remus go.
Remus leans into the touch, hands moving to twist into the material of Sirius's nightshirt as Sirius runs gentle fingers through soft strands, carding his fingers through tawny hair.
"You need to sleep," he says, even as Remus begins to shake his head. Sirius pushes him to lie flat on the bed, ignoring the soft noise of protest. "I'll stay with you."
Remus pauses, looking at him with large eyes. Finally, he nods. "Okay."
Sirius moves onto the bed and Remus shuffles over, and it's a few moments of blanket-adjusting and body-arranging before they're finally both comfortable, Sirius on his back with Remus's head on his shoulder, heavy and warm.
"Alright?" he asks, breath moving over Remus's hair.
"Alright," Remus sighs.
"Sleep," he says, fingers moving to twine in soft hair.
Remus moves his arm to tighten around Sirius's torso, followed by a quiet, "Thank you."
And as he presses a kiss to that head, Sirius thinks that he has never felt more content than in this moment.
