A/N: Prompted by the DA Kink Meme ( .com) and based entirely on my own head canon.
Charles Carson is an old man now.
He never seemed it before, when he was well and running Downton just as efficiently as he had done forty years ago, but his illness has stripped him of his vitality, but it has not stripped him of his spirit. He still smiles up at her with the same warm smile, only now Mary knows what lingers behind it, what has been lingering behind it for the last thirty years.
"How long have you known?"
"Known what, my lady?"
Mary smiles wanly. Even on his deathbed, he's trying to protect her. And now she knows why.
"I know you know me better than that, Carson." She sits down gingerly, eying the butler closely, seeing him for the very first time perhaps. After a long moment she reaches for his hand, and has to blink back tears at the fragility of his grip. "I don't need you to protect me anymore."
She has Matthew now, children that need her protection and an estate to preserve now that her father is gone...her other father.
Carson breathes in unsteadily and Mary tightens her grip on his hand.
"Her ladyship—"
Her ladyship is the one thing Mary does not wish to speak about, and for the first time she is glad her father passed away when he did. It seems churlish somehow, to regard her mother so harshly when the man in front of her is of equal blame. But her mother is not dying – she is living comfortably in New York with the late Martha Levinson's fortune and a devoted maid who is still too close to the Countess for comfort. Carson is dying, and Mary feels nothing now but regret.
"There's no need, Carson—"
"Your mother," Carson interrupts, in the sort of tone one might consider parental and it brings a lump to Mary's throat, "was lonely, my lady. Very young and very lonely and married to a man who could not yet see past her fortune."
Mary frowns. She has not heard this version of her parents' marriage: they were always so happy it sickened her, but it was possible it hadn't always been that way. There had once been a time she hadn't loved Matthew, after all, and that possibility seems inconceivable now.
"And you?" she asks, swallowing the lump of emotion with considerable difficulty. She had always been so good at masking her emotions – who had she inherited that from, she wondered, if not the grandmother that had never even been hers – but she can't help but falter now. "Why did you do it?"
Had he loved her mother? Sex was one thing – a bastard child concealed for decades was another, but love was a betrayal and her Papa might not have loved her Mama immediately if Carson's testimonial was truth – and to her knowledge he had never lied to her – but he had loved her eventually. He had loved her all those years in ignorance of the fact that his wife may have loved another man – and a servant at that – before their marriage had ever really began.
Instead, Carson offers her a wan, weak smile. "I was lonely too, my lady."
Mary nods. She knows very little about Carson, beyond the obvious and that he was once on the stage, but as far as she knew he had never been married. The only woman she has ever suspected he had feelings for is dead now.
"And...now?"
Carson glances subtly in the direction of the door, in the direction of the parlor that lay beyond, but it didn't belong to her anymore. Mary was no fool – she had been quite aware of Elsie Hughes' opinion of her and she had even shared it to a point, but they had always had Charles Carson in common. Her death had taken them all by surprise, but none more so than Carson.
"I've had a good life," he said finally, smiling weakly and brushing his thumb over her hand.
He's been waiting a lifetime for this moment, she expects, and Mary is glad she can give it to him.