Sirius knew that she was hurting, and he knew that the what he was doing for her wasn't enough. And as much as he wanted to help her, to warm her, to calm her fear, he was desperately afraid that he would hurt her more if he tried. But when her hand wrapped around his arm to pull him closer to her, all thought left him, and he was left with nothing but the instinct that had compelled him to protect her. He moved closer to her on his own, wrapping his arm around her body, covering her and all but pulling her up and into his arms. Words of comfort, her name, all soft and nearly silent were whispered as he pressed his cheek to hers as he fought to steady his own breathing.
Realization hit him all at once. There were so many questions running through his mind, so many things he wanted to say, to understand what was happening here. Just moments before she had been as still as the grave, quiet and unmoving, all of the bright and shining beautiful life gone out of her, and now - now - to him, she appeared to be fighting for that life, to be struggling against the pain of death, his name on her lips as she fought to come back to him. It was unreal, unimaginable, impossible in his mind, but yet undeniable. "Sweetheart," he said against her ear, for just one moment sounding a bit dazed. He knew he should get someone for her, he knew that someone else might be able to help her better than he could, but as good as his intentions were, and as much as he wanted to free her from the pain that she was in, his body wouldn't respond to do anything other than cover her, to protect her, as he had meant to do all along.