They sent his box of medals to Downton. She didn't know what they were all for, but she knew enough to recognise the Military Cross as she delicately fingered the cold silver hanging on its white and purple ribbon. The three cuttings of the London Gazette in which he had been Mentioned in Despatches sat dry and yellowing like fallen leaves at the bottom of the box. Cousin Isobel had passed them around the drawing room last night after dinner proudly, sadly, and it took Mary every ounce of willpower to smile passively and express the same heartfelt but generic sympathies as the others.

Letting go of the little leather covered box and passing it to Sybil next to her had been unspeakably difficult. Every instinct told her to cling to it, hold it to her and never let go, just as she wished she had done with Matthew.

They all knew what missing in action meant even though no-one was prepared to say it. He was not going to be found, mildly shellshocked and his memory blurred, in a Belgian field hospital as they all told each other would happen in confident, strident tones every day. He was not stuck, safe but stranded, behind enemy lines until help arrived. Just in case she had not been aware of it before, the war had taught Mary, taught them all, that life simply was not that kind.

No, in their hearts they all knew the truth. He had been blown into too many pieces to rake together and fill a grave with, or worse, was hanging, skewered, on a strand of barbed wire snaking its way across the muddy ocean of no man's land where no-one was able to bring him back.

She would have. She would crawl through the drowning mud, the unbearable cold, waves of artillery fire to reach him even if all there was left of him was dead flesh. With a bitter, debilitating regret, Mary knew now, far far too late, that she would go anywhere, do anything for Matthew.

She was in her bedchamber after another long, hard day. Every day was like that now, three and a half years into a war that everyone said would be over by Christmas but now looked like it might simply go on forever. Supposedly they were winning, gaining ground from the Germans with each battle, but she didn't believe it. She didn't believe anything anymore.

Sitting at her dressing table, she had watched in the mirror listlessly as Anna had unpinned her hair and carefully removed the glittering, meaningless jewels that she was draped with. She stood when Anna asked her to, for her dress to be unhooked and corset unlaced, but couldn't pay attention to her maid's chattering words. She knew the conversation was kindly meant, that Anna was trying to distract her from the fear and misery that punctuated all their lives, but it would take more than a comedic retelling of Mrs Hughes and Mrs Patmore arguing for the thousandth time about who should be in charge of the ordering of food, or that Daisy had had another letter from William and he was well, if not safe, and had just been made a corporal.

The second her nightgown was on, Mary laid her had on Anna's arm, halting her stream of consciousness. 'Thank you Anna. I'll be fine now.'

'Oh, I'm sorry Lady Mary. Here's me going on and you probably just want some peace and quiet.' Before Mary could respond, Anna had gathered up her things to take to the laundry room and slipped out of the door.

Mary didn't blame the maid. She knew that no-one – Anna, her mother, her sisters – really knew what to say to her anymore. It had been hard enough when news of Matthew's engagement had reached Downton, or when her scandal broke, but since Matthew had been missing, people could barely look her in the eye. In response, she had brought the shutters crashing down, shutting out anyone who so much as attempted to offer her the slightest sympathy or kind word. Save it for Lavinia, she had snapped at Sybil, feeling instantly guilty at the hurt on her innocent yougner sister's face. She's the one who has lost a fiancé. For a distant cousin like Matthew, we'll be into half-mourning by Christmas. Even Edith, usually so quick to criticise her for the heartless things she said, had given her a sad smile and turned away to comfort Sybil.

After that, they had left her alone to her heartbreak. Edith was busy on the home farm now there were no longer enough men to do the work, and Sybil had thrown herself into nursing from the very beginning and she knew they both disapproved of the way she had kept herself aloof. Edith had been having another dig at her over dinner over her lack of involvement and Sybil in her gentler, kinder way urged her to take part more.

What they forgot, in their enthusiasm to do their bit for the war effort, was that there was still an Estate to run. Obviously the house was ably taken care of by Carson and Mrs Hughes, but there were ten thousand acres and nearly a hundred cottages and farmhouses that needed looking after also. Their father had been in London for much of the war, and with Matthew gone as well, only the steward, Soames, had any idea of the things that needed to be done. Then conscription had come in and there was no-one.

Her curiosity had been piqued when the news came that John Drake, one of their tenant farmers, had been killed at Verdun. While everyone had been bemoaning the loss of a good man and heaping pity and gifts of food on his widow and children, Mary found herself wondering what would happen to the family next. His wife was a fit and capable woman, and her eldest son was ten, certainly old enough to be of some use around a farm. She saw no real reason why they couldn't stay there. If Edith could plough a field, Mary was convinced Mrs Drake would be more than able to.

So she had visited old Barratt, who had been steward before Soames, who was well into his nineties and lived in a cottage in the village. Painstakingly, and with obvious glee that someone was taking an interest, he explained the many things that needed to be done to ensure the smooth running of the estate. It wasn't showy like Edith and Sybil, and no-one really realised she was doing it, but cottage roofs still needed repairing and barn walls needed rebuilding even if finding the men to do it was a longer and more difficult job than the work itself. There hadn't been any shooting or hunting on the Estate since the start of the war and the pheasants and rabbits and pigeons and deer were out of control, attacking the much needed crops the second they poked out of the soil. John Drake was not the only tenant to have died, and new tenancy agreements needed commissioning to give grieving families some much needed security to set their minds at rest. Lord Grantham gave her permission to act as she saw fit and she set about bringing everything back in hand.

Her sisters assumed she spent her time riding around the Estate for her own amusement and she didn't bother to correct them. She wasn't doing it for the attention, but because it needed to be done. And because if she stopped thinking about the thousands of things that needed taking care of, if she paused for as much as a second from the endless litany of tasks she kept rolling around in her head, all her thoughts and feelings for Matthew came flooding back. Sometimes the grief felt like a blow to her chest that was strong enough to knock her off her feet.

When that happened, the only person she could tolerate was Carson. She found his deep, kind voice soothing and she didn't hear any criticisms lurking behind his words that she felt were there with everyone else. Sometimes she let her guard down in front of him but mostly she didn't, though he never treated her any differently no matter how she behaved. It was Carson who had found her on the bench under the tree, after her father had arrived home unexpectedly last month and called her into his library to bring her worst, worst nightmare to life. He had held her as she sobbed on his shoulder, just as she had after the garden party, and it was only Carson who seemed to truly see the pain she was in.

She had always been aware that she was cold hearted and dispassionate, but she knew absolutely that if Matthew was dead, so was she. Every last bit of emotion and love she had inside of her would die with him, as it was him who had awakened it.

He had opened her eyes to a different way of living, where marriage could be based on something more than a business arrangement. Of course, her parents loved each other but it didn't start that way and she had never imagined that for herself. When she had been engaged to Patrick, she remembered being vaguely satisfied with the neatness of everything and the prospect of becoming the Countess of Grantham, but it was nothing she wouldn't have given up for the shot at a Duke or Marquess.

Now though, the thought of being married to Matthew, of seeing him every day, sharing her life with him… Why had she not accepted him? She could put up with anything – a butlerless townhouse in Manchester didn't seem so horrific just as long as she was with him.

She had been stupid, proud, blind and now she was paying for it, though it was Matthew who had paid the ultimate price.

After the news came, Violet had waited three days before suggesting that in the absence of a male heir breaking the entail may be a more straightforward task. The idea that now, after everything, Downton might eventually become hers after all left Mary with nothing but ashes in her mouth and bile in her throat. If that happened, she would leave. Edith could have it all, every last penny. It all seemed so tainted now.

She felt tainted as well. Her body had been tainted years ago and now her soul was too. Tainted by mistakes and bitterness and the tragedy of love lost without hope for redemption. She felt like the scandalous Dorian Gray, with her outward face still unlined, beautiful and flawless except she had no hidden portrait to betray the damage on the inside.

There was a quiet knock at her door. Tearing herself away from the grim study of her pale, brittle reflection, she turned, thinking it was Sybil, who sometimes came after a particularly horrible day to sit quietly with her for a while. They rarely spoke, but the companionship was one of the few things that made Mary feel just about human again.

'Come in.'

Tentatively the door opened, but it wasn't her sister who took an uncertain step into the bedroom.

'Carson,' she asked in surprise. 'Is something the matter?'

The war had changed a lot, but nowhere near enough that a butler should be in the bedroom of the daughter of the house, and Carson's discomfiture showed in his face. Still hovering by the doorway, he said, 'I am terribly sorry to disturb you my lady, but I thought you would like to know straight away. There has been a telephone call from Lord Grantham.'

'Yes?' Her heart pounded out of her chest, the blood rushing in her ears like a torrent. What now? They could not bear any more bad news here, the little band of them left behind. Fear gripped them every day – the conversion of the house to a hospital kept them busy enough to deaden it at times, but they went to bed every night with that fear redoubled on account of the things they had seen. Who was it going to be this time?

Then Mary suddenly realised that Carson did not look like the tired, beaten man he had every time a fresh piece of tragic news had hit them these last three years. When she looked at him, he was smiling.

After a moment's deliberation, he came towards her and grasped her hands tightly in his own, kneeling before her. 'They've found him Mary. In a field hospital in Ypres. They've found him.'

'He's alive?' Her voice was tiny, and childlike with disbelief and the reignition of dead hope.

'Yes. Lord Grantham did not have many details, but it appears Captain Crawley was injured at Passchendaele last month and was taken to a nearby field hospital where he was been ever since. His identification tag was missing apparently, and he…' For a second, Carson faltered, watching Mary's expression carefully. 'He is suffering from shellshock and cannot remember his name. His Lordship has been sending photographs all over Europe and finally he received a response.'

'Oh Carson, I…' For a long time, she stared back at him with eyes glittering with tears that she had forgotten how to shed. Then doubt flickered back across her features. 'They are sure? They are truly sure? I couldn't bear it if…'

'They are sure,' Carson replied, and his deep rich tones calmed her. 'I would not have told you if Lord Grantham had not been sure.'

'Oh, thank God. Thank God.' She felt hot tears finally breaking free and trailing unevenly down her cheeks, but she was unaware of anything beyond the enormous wave of relief that diffused through her. He was alive. Alive.

'Miss Swire is to be telegraphed with the news,' Carson said cautiously.

'I don't care. He is alive Carson, that's all I need. I just need him to be alive.' There was such fire and happiness shining in her eyes, the old butler wondered how anyone could have ever doubted her love. It was etched into her every feature.

He squeezed her hands again, and she smiled in return. 'He is to come back here of course,' he said, 'to recuperate. Apart from the shellshock, he has a broken arm and a few minor injuries, but nothing that will not mend, by all accounts.'

'Have they said anything about his memory?'

'No, but I understand that once men get away from the source of the trauma, things often improve in a more restful environment.'

Mary nodded. 'I hope so, for his sake. And Cousin Isobel. She must be so happy, so relieved. And my father, I know he has been dreadfully worried, for Matthew of course, and for Downton as well. It isn't thought that there is another male heir after Matthew so goodness knows what would have become of things.'

'Do you ever think of yourself Lady Mary?'

She thought about the question. 'Not often, not anymore,' she answered truthfully.

With a small grunt of effort, Carson rose to his feet and patted her gently on the head as if she was still six years old. 'You will make an excellent Countess, my lady.'

'Oh Carson, you don't mean that, not now. Not after everything. Matthew is alive, and coming home to Downton. That is a better outcome than I could ever have dreamed of five minutes ago. It is more than enough for me.'

Carson opened the door, and made to leave, but at the last moment, turned around and smiled at her as enigmatically as a practical old stalwart like him could manage. 'Mrs Hughes has suggested to Lady Grantham and Mrs Crawley that perhaps Miss Swire not be sent for straight away. That perhaps it will all be a little traumatic for a while and that Captain Crawley might do better if he is allowed to settle back into Downton first.'

Mary frowned. 'Why has she done that?'

'Haven't I always told you Mary, we're all rooting for you.'