There's something about Matthew and Mary in a period without all of the tension that's harder to write, maybe because we have yet to see them actually together. I hope this stays true to the characters, and to what you imagine their relationship to be.
It was the chill that woke him—a gust of frigid air from an English November that brought the temperature down in an instant and rustled the lighter fabrics in the room. The weak light from the moon illuminated a few surfaces—a smattering of their duvet, a few inches of a writing desk, the mirror at Mary's vanity. He followed the line to the window, where an almost ethereal glow encompassed the figure of his wife, her cream nightgown billowing in the slight breeze. Her hair was down, as it often was at night. It would make another person look vulnerable. But Mary, as he knew, was never so visibly vulnerable in the face of a storm.
He watched her silently for a few moments, but when the cold became almost unbearable for him, he wondered at how long she'd been standing there in her rather unclothed state, and rose, gathering both their dressing gowns as he stood.
He was not sure if she noticed his approach, but she didn't react. He lifted her gown gently onto her shoulders, and lingered only long enough to make sure she had a good grip on the garment. His hand brushed across her shoulder in comfort as he eased back.
She turned to give him a brief and unconvincing smile.
"I'm all right," she answered his unspoken question.
He stayed silent and watched her draw the dressing gown closer around her stomach-an odd, nervous gesture for Mary.
Waiting, though, as he'd discovered long ago, was the best way to get the truth out of Mary.
She added, "I was just having trouble getting to sleep," as though that would make her previous claim more believable.
"Yes," he said softly. He leaned against the table just behind them and watched her as she contemplated the night sky, her head shifting around randomly but not aimlessly.
"What is it, Mary?" he prompted after a few minutes of silence.
She glanced in his direction, and seemed to remember that she was speaking to Matthew, and so did not want to use and would not be successful with subterfuge.
"Do you like children, Matthew?" she asked, suddenly.
"I—do I…" he trailed off. He'd suspected for a few days, of course, had assumed she either didn't know herself or was waiting for some sort of confirmation to tell him. But could it be that her own insecurity was the cause of her hesitation?
He stepped forward and gently pulled her to face him, his hands coming to rest on hers, which had settled seemingly unconsciously to her stomach.
"I've not had much experience with them," he replied truthfully.
Her eyes turned back to his from the window, and suddenly there was an unmistakable mark of vulnerability.
"Neither have I, except I suppose with Sybil."
"Well, if your relationship with her is any indication, you'll be wonderful with them." She didn't react to him dropping the conditional tense.
"You really believe that?" she wondered, and he recognized the voice she used when she was angry with herself. So she had settled into wanting the role, without believing that she could be good at it. "I'm so cold, and bitter, and—"
"You are not, Mary," he argued, kindly. "Not with me, or Anna, or Sybil, or your father, or anyone else who takes the time to get to know you."
"You say that because you allow yourself to always feel your heart," she contested, sliding one palm onto his chest, against his heartbeat.
He tilted their foreheads together gently. "I always feel yours, too, Mary." He took her hand in both of his and ran his thumb against her wrist. "Tell me," he whispered. His voice was full of nothing but warmth and patience.
The fact that they were alone, and so close, at night, somehow made the phrase easier to part with. She shifted their hands off of his chest and onto her stomach, his hands beneath hers. "I'm pregnant," she whispered. Her eyes searched his cautiously.
He smiled, wider and wider each second. A delighted chuckle escaped his lips. He saw something in her expression shift, and at last, they were laughing together. She wound her arms around him, buried her face in his neck. Her dressing gown slid off her shoulders and onto the floor as her hands framed his face and they kissed in the moonlight, breathlessly, savoring the way their hearts seemed to beat in sync for just a moment.
He pulled back and pressed his lips to her cheek, her forehead, her mouth, and finally her stomach.
He stood again, a hand cradling her neck. "I love you," he said, their gazes locked.
His excitement, as it was bound to, began to melt away the insecurities that she had built around herself. She allowed herself to feel a little of the anxiety, but for the first time since she had awoken almost an hour earlier, it did not outweigh the joy.
"You must be freezing, Mary!" Matthew broke the silence, at once slipping into a protective mode which she supposed she would allow to last with their children but which she was most certainly going to train him out of with respect to her in the coming weeks.
She felt her arms as though she was noticing the temperature for the first time. "I'm all right," she concluded.
He raised an eyebrow in challenge.
"I mean it this time," she added. She paused, studied him. "What is that glint in your eyes?" There was mirth in her voice.
He shut the window silently without giving her an answer, though he was smiling. Then, he lifted her off the ground and into his arms. "Matthew!" she cried, laughing, "What are you doing?"Her hands wound around his shoulders, and her head fell against his neck in exasperation. He spun them around once. "Matthew Crawley," she sighed, shaking her forehead against his skin, "I am perfectly able to walk, and you are ridiculous."
He laid her down gently on their bed without comment (unless his smirk could be taken as such).
He laid on his back next to her and she shuffled closer. "You're happy?" he wondered. His fingers trailed aimlessly on her neck as he waited for her answer.
She smiled and kissed his collarbone where her head was resting. "Yes, I rather believe I am."
He smiled back, kissed the top of her head. "So am I."
Her palm brushed against his chest, his familiar heartbeat and warmth reassuring. "I never doubted you would be," she confessed.
He pulled her to him for a kiss, his grip lose around her elbow. Her fingertips trailed along his arms and shoulders, her breath warm as it dusted over his mouth. They kissed languidly, breathed deeply.
When they were both gasping for air, he pulled away, pressing a kiss to her forehead as he rested back against the pillows.
"We're having a child, Mary," he wondered, his gaze drifting momentarily to the ceiling.
"Mmhm…," she assented. "Given our history, I wouldn't be surprised if we have nothing but girls," Mary commented wryly.
His hand began to run up and down her back. "I wouldn't mind."
He saw her brow furrow even from the odd angle.
"And the Great Matter?" she inquired. His hand paused.
"The world is changing. Our daughter won't need to marry a middle-class lawyer from Manchester in order to inherit."
Mary swatted at his chest. "Matthew," her tone on his name was long-suffering, but then it softened, "you know perfectly well, that had nothing to do with it."
He smiled fondly and amended his first line of reasoning, "Well then, our daughter won't have to marry a sea monster."
"And what problems could the children of Perseus possibly have that would require marriage to such a creature?"
He laughed and pulled her closer, feeling her grin against his chest.
They were silent for a moment.
"For a while, I thought I had missed out on this," he said, so softly it was almost a whisper.
Her head rose and fell with his breath. She sensed that he was not looking for a response to his recollection of a painful time not too long past, and stayed silent. She kissed his collarbone once more, twisted their fingers together, drew their joined hands one last time to her stomach. "Goodnight, Matthew. I love you."
He broke from his musings soon enough to bring the hand that held his to his lips, and pushed all but the best things out of his mind. "Goodnight," he whispered. She was already asleep.