A/N: SPOV
If Severus were a good man, he wouldn't have been listening in. But he was who he was, and he was concerned for her first and foremost.
Lupin wanted to talk to her, but kept pushing her away. The young witch's emotions aren't some sort of muggle yo-yo for someone to play with and not expect any kind of backlash.
As he stood by the door, her words hit him with a level of honesty that she might not ever want to admit to him in person. He used the same listening charm that the Weasley Twins developed for the extendable ears, knowing that it was probably inappropriate but wasn't concerned with the moralities of others.
"That's not good enough." Tonks whispered, almost hoarse with pain. "You know where I stand Remus, but I don't know where you do and obviously neither do you. When you finally figure that out let me know." He heard her footfalls grow louder, so he ended the charm and sat himself by his brandy.
She strode in, and her sweeping gaze fell on Severus as he kept his eyes on the periodical in front of him, waiting to see if she was going to say anything. She looked to the door and resigned herself to face a bookcase, with her back towards him.
Severus put down his reading, sipped his brandy, and silently locked the door with his wand.
How do I approach this? He thought idly, knowing that she wouldn't want to speak about it. He approached her slowly, and saw her tense up slightly.
"I locked the door; you need not speak up about it if you do not wish to." Dare I do this? He swallowed hard, and took a breath before he continued. "I would like to take your mind off of such matters, if you would allow me, Nymphadora."
After what felt like the longest pause in his life, she had responded with a curt nod. He raised his hand and threaded it through her hair, clamping onto a fistful. With a sharp tug, he pulled her into his arms and embraced her tightly.
"I promise to do all that I can to make you feel safe, wanted, and desired. I am willing to do this as your Dominant, to take away the burdens of your life, no matter how temporarily, so that you can be happy. Even if for only mere moments. I will be here for you." Releasing her, her spun her around roughly and pinned her against the bookshelf, locking eyes with hers. He let his mask fall and showed her his desire and his sheer force of will. He closed the distance between them, his nose grazing hers as his lips were mere millimeters from hers.
"I wish to take you in so many ways, and to have you serve me in ways that you've only dreamed of in your most wicked fantasies. Such frank and open honesty from me is something that few ever get to see, but is the one thing that I can offer you as your Dominant."
His body was demanding that he kiss her, but he knew it would be pushing her too far. It would be her decision that mattered, not the raging insecurities of an unworthy man that kept pushing her away yet pulling her back for more emotional torment.