A/N: My first (and likely to be only) Downton fic. It just refused to get out of my head. Other people have done it better, but oh well. :-)

If Not For Isis.

It was that damned dog. He'd been a fool about it, he knew. Just one more example of his remarkable capacity for throwing his whole life away in a single moment's insanity. The insanity had a name. Its name was Mary.

Facing Lavinia had been the worst thing. He'd felt an utter cad, sitting beside her sick bed talking of their wedding when he knew . . .

"I heard – everything. I saw everything."

The memory of it tormented him. Lavinia – her disappointment, her vulnerability. Her almost total lack of surprise.

And yet, he was tormented still more by the thought of Mary. He despised himself. Despised the way that even now, he could not stop thinking of her; of the warm, beguiling softness of her mouth; the smooth skin, the bunched muscles of her back beneath his hands; the sheer abandoned exaltation, or insanity, or whatever it was between them that held them both in thrall. Knowing only that this was good, this was right; glorious oblivion crashing over him as she kissed him with all of the power, and passion, and rage that was theirs, and theirs alone.

And then . . . that small, shy voice, like a blow to the stomach.

And Lavinia – dear, sweet, child-like Lavinia – had offered him a way out.

"Perhaps this is a second chance..."

And that, of course, was the one thing she could have done to make sure that he could not go back on his word. Because if she still loved him, and he had given her his promise, then, as a man of honour, he could not retract it now. A tiny, spiteful part of him wondered if she had done it deliberately. And he hated and cursed himself for the tiny, rebel shoot of hope that had flared in him at those words.

Matthew sighed, bowing his head into his hands. With bunched fists, he scrubbed tiredly at his eyes and aching temples... such a day. Such a long, draining day. Leaning back in his chair, he fumbled in the pocket of his dinner jacket, and withdrew the small stuffed dog that had been with him to hell and back. He considered it momentarily. Shabby and tired-looking, the cloth worn thin, bits of the stitching coming loose near the tail. It was a grubby sort of off-white, the black glass beads of its eyes so chipped and scratched as to seem almost opaque, its features fixed in a vague, amiable expression. Matthew propped it against the corner of the mirror on his dressing table, and subsided back into his chair, glaring at it.

"This is all your fault," he told it, accusingly.

He had managed so well, up until that point. So well, that he'd managed almost to convince himself. Right up until the morning when his mother had come downstairs with the damned dog in her hand.

"Is this yours? Only I didn't recognise it . . ."

"It was given me as a charm. To take to the front." Lavina's head lifts from her embroidery, her attention on his face. He fights the urge to grab for the toy, struggling to keep his expression inscrutable.

"Oh well, I might as well take it down for my refugees . . ."

"No!" The word is out before he can stop himself. He snatches the dog from her, stuffing it hastily into his pocket, unpleasantly aware that his face is flushed, and that they are both watching him with altogether too much sympathy and understanding in their eyes.

Since then, the dog had somehow managed to make its way back into his pocket on a daily basis.

Absent-mindedly, Matthew reached out again and picked it up, turning it in his hands as he'd done so many times before. In the trenches, the men had all been accustomed to it – Captain Crawley sitting by the hour when business was slow, turning the stuffed dog silently between his hands. It wasn't uncommon. Most of the men had something. Usually, it was a photograph – in a locket, or a frame, or pressed inside a book; sometimes it was a lock of hair, a crucifix, a letter, a ring. A watch, a knitted scarf, a cigarette case, a string of rosary beads . . . For Captain Crawley, it was a small white dog.

It had become a mascot, of sorts, for the motley battalion. Everyone knew that the last thing Captain Crawley did before he left the dugout was to pocket the little toy. Superstitious, foolish, childish as it was, Matthew had never been able to shake the habit. The men got used to seeing it every time they stopped on a march, and during every lull in hostilities. The dog was lucky, they reasoned. If nothing bad had happened while Captain Crawley was carrying it, then so long as he carried it, nothing bad could happen. Never mind that various of their comrades got shipped back up the line in pieces every few days – as long as Captain Crawley was there, they were all ok. William had nagged and nagged Matthew to think up a name for it, and eventually, in desperation, he had christened it Isis, reasoning that William would understand it to be a memento of Downton, hopefully without drawing too much attention to who had given it to him.

Somehow though, the story had leaked out. William must have guessed more than Matthew had thought, and William, of course, could no more tell a lie than he could fly to the moon. And yet, somehow, strangely, Matthew had found that he didn't mind.

The trenches are a maze, before you're used to them. Matthew picks his way slowly around the perimeter, making one final round before bed. The guns are quiet; only a faraway crackle of artillery, which from this distance is muted, almost restful, like being underwater. The stars are bright above him, and they glint on the razor wire far out over the plain. As he approaches the tin shack which the men call the canteen, he can distinguish William's voice amongst the low rumble of conversation. He hears the clink of a bottle, and watches as the red glow of a cigarette passes from hand to hand. Private Mason, Private Carter and Corporal Harvey, talking quietly to the two new men from up the line. Matthew is tempted to join them, when he is brought up short by the mention of his own name.

"Where'd it come from?"

"It's Captain Crawley's. I reckon Lady Mary gave it him. "

"Is she his girl?"

"No . . . No, not any more. Though she were – or leastways, I always thought she were, but now I can't rightly say. You know how it is, for fine folks. They can't just out an' say it . . . It's harder for them than it is for us."

"What's she like?"

"Well, she's a fine lady, right enough, and awful pretty. She's got a tongue on her like razor wire, though she don't mean no harm by it. And she's sad – near always, it seems, these days, but she's kind too, kind where it counts. When my Ma were dying, Lady Mary got to hear of it somehow, though Ma hadn't told me, nor written, nor nothin'. And Lady Mary, she just says to me 'William, I think you should go home for a few days. I've fixed it with Mr Carson'. So I got to see my Ma before... you know... before the end, like. I helped Lady Mary with her horse when he were lame, a whiles back - she's got a great black horse called Diamond, and she's that soft on him that you wouldn't believe."

"Well, she's got an admirer in you, and no mistake."

William falls silent, perhaps abashed by how much he has said, and it is not long before the conversation drifts elsewhere, the glow of cigarettes dancing like fireflies on the back of Matthew's eyes.

Later, in the dugout, he speaks to William about it.

"I heard you talking about Lady Mary, William."

William looks awkward, slightly ashamed, his head bowed in expectation of a reprimand. "I'm sorry, Sir. I didn't mean no harm by it."

"No, it wasn't that . . . it was just . . . the way you talked about her. I suppose I'd never really thought about it before. But she is kind."

"She is that, Sir, though I think she doesn't much like for anyone to know. But, she takes up a cup of tea to Mr Carson when he's feeling poorly, and she's been such a help to poor Anna about Mr Bates. And then, when Lady Sybil went into Ripon she stood up for Mr Branson to his lordship, told him it weren't Mr Branson's fault."

And Matthew thinks of Mary's unlooked-for kindness to Lavinia, her cool dismissal of Cousin Rosalind's attempts to stir up scandal. He feels ashamed.

"Yes . . ." he says, horrified to discover the tightness in his throat. "Though of course," he adds, for William's benefit "she's always been perfectly beastly to me. Tossing my hat into the pond, and suchlike."

William grins, but Matthew's thoughts are already running on.

"William?" he asks, hesitantly, wary of the unfamiliar ground "Do you . . . Do you love Daisy?"

"Of course," says William, instantly. And it is as simple as that. Because for William, everything is simple. There is one girl to whom he has given his heart, and if you love someone, you tell them, because what would be the sense in delaying?

"But how do you know that she loves you?" Matthew asks, feeling adrift, like a child, in the company of this shy, unlearned and infinitely wiser man.

"I just know," says William, simply. "I don't know if – if it's for keeps, like. But I know that, if I was ever wounded, say – well, I just know that Daisy would be there waitng for me when I woke up."

"Yes . . ." says Matthew again, and his voice is tight. And he thinks that William is luckier than he knows.

Matthew leans against the wall of the dugout, with the coppery taste of blood in his mouth, and the taint of earth all about him. The small white dog is in his hands, and he turns it over and over between them, caressing the thin woollen ears between finger and thumb, tugging gently at the poorly stuffed limbs. He thinks, but not of the war. He remembers thin white wrists, and frail shoulders, the elegant curve of a neck; skin like silk beneath his fingers. She is not like other girls he remembers. Other girls smell of lavender, or rose-water, or expensive perfume. She smells of sandalwood and pine trees, clean and cold, like autumn leaves and rain. He tells himself it is Miss Swire that he thinks of. Only occasionally, he catches himself out, his memory an image of immeasurable dark eyes.

He glances sideways to the desk where Lavinia's picture sits. There has been no mail for several weeks now. His mother and Lavinia write weekly, and he receives them sometimes weekly, sometimes monthly, sometimes not at all, and never in the order written. Mary writes more seldom. Her letters are terse and funny and heartbreaking, as contradictory as their author. She addresses her letters 'To my dear Matthew'. He signs his 'From your loving cousin'.

Matthew dropped Isis back on the dressing table, and stood abruptly. All this was getting him nowhere. It was late, he was tired, and he was supposed to be getting married in two days, though it was looking less and less likely with every passing moment. He had never wanted this. Any of it. He was a lawyer from Manchester, who had wanted nothing more than to try to do some good in the world. Angrily, he shrugged off his dinner jacket and discarded it in a corner. Unfastening his cufflinks, he drew his shirt off over his head without bothering to undo the buttons. Molesley would make him pay for that in the morning, he knew. He tried not to look at the body in the mirror – at the pale chest, striped unevenly with old wounds, and the thick, ugly band of scarring across his spine. Even his body was not his own any more.

The rest of his clothes discarded, Matthew drew his pyjamas on awkwardly. The elastic at the waist scratched on the thickened tissue at the small of his back. After six months, he still struggled to bend, or to reach behind him. But Lavinia had said "You can lean on me," and he had leant on Mary instead. He felt sickened with himself. Lavinia had offered the greatest sacrifice she knew, and he had not wanted it. He had never wanted it. Not since the day in the hospital, when he had sent her away from him for good.

The first time he wakes, his eyes remain closed. The first thing he is aware of is the absence of noise. There are no screams, and no guns. There is a familiar astringent, antiseptic smell, but for a long while he cannot place it. There is a warm light on the outside of his eyelids, but he cannot remember how to open them. Half in a dream, it seems to him that he hears Mary's voice, talking to him from a long way off.

The second time he wakes, he is conscious of a pain in his lower back. He opens his eyes, and Mary is watching him. She smiles, and there are tears in her eyes.

"Matthew darling."

"Mary."

He realises that his hand is clasped in both of her own. He presses her fingers gently, and her hands are shaking as she clasps his tighter still. He drifts again, his eyes closing, a smile tugging at the corners of his mouth. He is home.

"Matthew darling, Doctor Clarkson is going to come and look at you. Can you try to answer him for me?"

He makes some muffled reply, filled to the brim with morphine, and exhaustion, and love.

The third time he wakes, Mary tells him that he will never walk again.

Somehow, Isis too, has survived the war. He finds the little dog lying with his neatly folded uniform in a pile beside the bed. The damned thing has lost half its stuffing now, is grubby and faded in equal measure. He remembers Mary telling him to return it to her without a scratch. He feels a fool.

His lucky charm lies on its side, exactly where they left it, poorly stuffed legs incapable of supporting its weight. His body is immobile, but he turns his face away.

They sit in the grounds, where they used to sit before the war; an age ago it seems now. Mary on the bench facing the spreading beech trees and the smooth sward of grass, Matthew in a wheelchair beside her.

"You must have lots and lots of children," he tells her. "Six sons at least. Then I can be lord of the manor, and make them carry me everywhere in a sedan chair and vie for my favour."

She raises her eyebrows. "And six daughters as well, I suppose?"

"No, daughters cause altogether too much trouble. The women in this family are all dangerous rabble-rousers, hadn't you heard?"

"And the men are all conceited prigs. Or sea monsters."

He laughs at that, and for a moment, the light dances again in his blue eyes.

It is November 11th, 1918. Mary's hand is warm in his own as they laugh, and his tears are her tears, and his pain is her pain. Isis is a familiar shape in the pocket of his jacket, as Mary threatens once again to push him into the lake.

It is November 11th, 1918. William is dead, and Matthew is broken, and Mary is engaged to Richard Carlisle.

But it hadn't ended there. No. Cousin Cora had written to Lavinia, and Lavinia had come dutifully when called. Isis had finally been banished, tucked away in the back of a draw. Matthew had healed, and tried to forget, and to be content with a life that he hadn't expected, and knew he didn't deserve. Lavinia was gracious enough to believe him when he told her that he loved her, and only Cousin Violet had dared to challenge him. And that would have been that, and Matthew would have walked down the aisle of the church on his own two legs if it had killed him.

And then Molesley had discovered the bloody dog, hidden pathetically amongst a tangle of socks and ties and collars and handkerchiefs.

He had been managing so well . . .

Matthew pummelled his pillow with both hands, his back aching, pyjamas prickling intolerably against the scars. Still, sleep would not come. In the dim blue light from the open window, the dog stood propped against the mirror, as scruffy and pathetic as ever, its expression still vague and amiable. Matthew twisted restlessly, his mind still full of Mary's face, Mary's smile, the smell of autumn leaves and rain.

It was all that bloody dog's fault, he swore to himself. If not for Isis, then none of this would have happened.