Disclaimer: Characters and scenario taken from the Call the Midwife 2013 Christmas Special. I'm a visitor in their world.

You have been here before, mute and inert, conducting a vigil by a bed while your life crumbles. You know the cold of this slow dread. It throws a lengthening shadow until its silhouette suffocates. Every breath you drag from yourself crawls into its freeze, each time aching to become a screaming howl. Unseen and unspoken, that gaunt memory haunts you. You have been here before.

But then at least you could hold her hand. You watched the slow rise and fall of her chest and listened to her sluggish breaths. Now you cannot even do that. Only in imagination can you see the beloved little body which came jointly from her flesh and yours, now mummified in a metal cage with just the thin face exposed. It lies straight and unnatural against the pillow; it never lies like that when he is sleeping, but is always cricked on its side or twitching and shifting. The stretched paleness you recognise, but not from him: it blossomed on her too.

Your only consolation is to run your hand through his hair. Its texture is turning, leaving the fine softness of childhood behind. You laughed when he asked if he could wear Brylcreem, teasing him for vanity and claiming it was justified to ruffle his hair there and then if he planned to start filling it with sticky mess. You and Shelagh chuckled about it later, saying this was the beginning of the end: soon it would be a guitar rather than the violin, then a quiff, winkle pickers and a girlfriend. Tracing the contours of his forehead under your fingertips and murmuring his name again, willing him to come back, in this moment you would grant him any request and feed any affectation.

I suggest you take it one hour at a time. You have no sense of how many hours have passed or what point in the night it now is. It is some time in the morning. You don't know when. You do not care. The hours march with brutal regularity. The power that spins and measures them also neither knows nor do they care. No change. No alteration.

Once more the desire to thrash your head against the machine comes as the same question throbs within you: how did I fail to notice? Once more you sit, immobile.

Then the second thought recurs. The people I love are cursed.

You thought it before when McGuinness' fat finger pointed out the lesions on the X-Ray, calmly talking of treatments and likelihoods of recovery while you reeled. You thought it again as you sat in the car thinking of Sister Bernadette while rain drowned the window screen, remembering when and why you had sat like this before, berating yourself for the insane stupidity which made you force yourself upon her and barred you from even the bitter joy of comforting her in her suffering as you could have done a few short months earlier. It was him who pulled you from your wells of self-pity, just as he did before when it was her. His vitality, his humour, his inquisitiveness, his love for what you were both losing, even in the worst of sorrow he gave you a reason to endure, if only to fulfil the promises you made to her: I will protect him, I will always keep him safe, I will love him even more because he will be what I have left of you.

How much you have failed in the first two promises. How much you know the truth of the last.

You were looking for polio throughout in the district, watching everywhere, alarm intensifying with each new case. How did you overlook the case within your own home, battling with the board with ever increasing fervour, yet so wilfully blind to your own disintegrating child? Was it stupidity, neglect, heedlessness? Wallowing in your own blasé happiness, your only sensitivity reserved for Shelagh and the drifting undertow of her anxiety? Or hubris? Nothing will stand in the way of this wedding.

The words dance and tumble into a new formation: I curse the people I love.

"Mr. Turner? Can I get you anything?"

It is the nurse. She is a sweet-faced girl. You heard the gentle mumble of her reading to the child two beds away earlier and she moves with night-time hush around the ward. Despite the preposterous uniform, something in her earnest simplicity is faintly reminiscent of Cynthia Miller. You stare at her blankly, registering finally that she means you despite the inaccurate title. You try to decode each sound which came from her mouth. White noise. It makes no sense.

She tries again. "Can I get you anything? Would you like a glass of water? Or a cup of tea?"

Slowly you begin to comprehend. "No." Inconsequentially, you wonder how a nurse on duty could obtain a cup of tea for a visitor. Perhaps she has a break. "Thank you."

"If you'd like anything later please ask." You give a heavy nod and blink as your fumbling brain tries to catch up with what she has said. "We've got some books. They're mainly for the children," she smiles tentatively. "There's a copy of A Christmas Carol though."

Although you are dismissing her, you hope she sees a glimmer of your appreciation. "Thank you, Nurse."

Have you read it? You do not think you ever have, but somehow you know that line, or an approximation of it. It never burnt so starkly until now: Spirit, tell me. Will Tiny Tim live? Live on, blessing those around him but struggling always with a crippled body, or die and leave the father broken beyond repair? Can the time yet to come be changed?

You stare again at the machine, hear its low and ominous hum.

"Nurse." You call her back and she is there, alert and keen. "There is one thing: the lady who brought my son in, she was sent out by the sister because she wasn't immediate family. I know that there are rules, but she is my fiancée. Timothy's mother, my first wife, died two years ago. Please, could she – "

Before you finish the request she starts to nod. "I'll write a note for whoever is on duty when she comes back." She lingers beside you for a moment, then speaks again, not looking at you, but him. "It will be lovely for your son to have a mother again." You note the use of the future tense and know what she is trying to do. You have tried it often enough yourself with patients on the cusp of despair. "When are you due to get married?"

The brief exhalation as you raise your eyebrows is quiet, but audible, a strange amalgam of disbelief and bitterness. "It was supposed to be today." You turn back to your son and stare. You are both paralysed now. When you look back, the nurse has melted away. She is at the desk, writing, and she looks as though she is crying.

When it will happen, you cannot imagine now. What is yet to come is as grey and filthy as it was in the autumn, encroaching tunnels whose destinations are hidden by the spectral hand of the present. Your need for Shelagh is a physical ache and you desperately wonder when she will return. You left her behind the window, as close as she was allowed to be and capsizing with anguish, and rushed past her in terror; and when you looked back, she had vanished. You have seen her in so many moods – briskly efficient, bubbling with laughter, twisting with indecision, resolutely courageous, luminous with joy – but that abandoned, uncontrollable grief you had never seen before. She was beyond you, you still trapped in shock and disbelief, unable to make sense of the garbled message which had come to the surgery. But her blind agony foreshadowed what you feel now.

Let her not be alone wherever she has gone. Let her not have returned to the silence of the house, where whatever horrors she experienced when she found Timothy will still be raw and cruel. It is not her home yet, only a strange and alien place made beautiful by hopes which are so fragile now. Yet she has no other place where she can go. Once more you wish she was not so imprisoned by guilt and had accepted the hands of love her sisters hold out to her still, rather than letting the wall of estrangement solidify. You could have done more to be the bridge between them; you know she will never be whole until this wound is healed. After all these years, in a strange way you are oddly closer to Sister Julienne now than you have ever been, knowing the sincerity of the affection you share. It has hurt you to watch her slowly bleeding with grief.

Maybe if they hear, Sister Julienne will still go to her. Perhaps Chummy Noakes. The news will pass from mouth to mouth to mouth to mouth to mouth.

His mouth does not change. Every muscle is frozen. It is this stillness which terrifies you most. He resembles a carved effigy placed upon a child's tomb. In life he was, is, never still. He is always rolling his eyes, fidgeting or squirming, scampering from place to place. His energy exhausts, but invigorates you, his laughter deafening, but rejuvenating. Vividly you remember the hapless practices for the three-legged race, how he dragged you on, intoxicating you with the draft of his enthusiasm, and how you laughed at his impatience as he looked forward to the race itself.

You let him down then too.

You could not say no; the woman was desperate, so many children she could not bear one more and even a butcher's mutilation was preferable. But for that you walked away from the only child you have and when you returned you had missed your chance and could only offer cheers from behind a rope on the sideline. Although you listened when he prattled and boasted in the car on the way home, you responded with only half of your stunned mind, the rest absorbed by what had happened afterwards. Your keenest attending was to the artless comments he made about Sister Bernadette, not to the account of his victory. And he will never run again, not like that.

That knowledge is another ghost. It haunts you too.

Why did he not tell you? He could not have been reduced to so pitiable a state and not have felt a single symptom. Had he told you, would he have been like Jack? Out of bed and giving cheek. Twelve hours ago that news would have been a dear relief; in this grim present it is a sneer. It is wrong that you briefly wished you could substitute your patient for your son if you could. It revolts you that you thought it, but it is the truth. You would substitute yourself first: if you could breathe for him, you would. But all you can do is wait. The bald facts you learnt at medical school are pointless in this moment, incapable of curing either him or you. Unanswered, the questions roll and rattle: why did he not tell you?

It's only a graze. You're always at work. Learn to be independent. One day you might be on your own. What about me?

You know why.

You were busy, always busy. But from the moment when you first heard his bold declaration of life call to you from the bedroom above you, he was the greatest gift you had ever had, yours in a way in which not even a wife could be, and you were utterly besotted. Did he not know? Even now, preparing for the event which should come with morning, it was always, always, about the three of you. It had been from the moment she first became herself for you by telling you something of herself: it was as a way to help you help him. Then she soothed his injury and took your place beside him when you were not there. Without a third of your lives, how can the two remaining share it?

The hours of the night pass. The cage remains, moving yet unmoved. On the regularity of its metal innards, on its impassive mechanical wheeze.