This is AU after Ep. 3.7., and it was written before Ep.3.8., so out of canon now. The relevancy of these nightly talks depends on your imagination of how the events could have progressed before the adoption. The characters of Patrick and Shelagh are not anymore the same ones as in Songs of Bernadette or The Marriage Vows. My apologies for my non-native English, as ever.
The Dark Night Of The Soul, part 1
It was 3 am. Shelagh had woken up and seeing that Patrick was not beside her, she went downstairs.
He was leaning unto the kitchen sink and nibbling a biscuit, in his pyjamas and bathrobe. There seemed to be a tea pot nearby and a tea-cup that didn't look very inviting. Shelagh thought he has just warmed up some water and added it to the teapot from last night.
Then he saw her looking at him through the kitchen hatch. He turned around, seemingly unable to meet her gaze and that turn was so abrupt that the cup fell into the kitchen sink.
"Oh bloody hell." He picked up the cup. "At least it is not broken".
He didn't turn to face her and he was breathing heavily. There was a forlornness about him that Shelagh was nearly frightened to see. But she was a bold girl. At least she said that to herself. She walked into the kitchen.
"Patrick, are you turning your back on me because of me?" she queried, hoping to catch him by this phrase. His state of mind was unknown to her. But she had to try.
"No, Shelagh." His voice was weary." At least, I don't think I am. It is not you. It is not because of you."
She came closer and put her arms around him from behind. He didn't push her away, but his head was sunk and he was immobile. Finally, he put his hands on her hands. He released her arms and turned slowly to face her, still keeping her hands in his. His face was oddly passive for a person so much in pain. Only the lips were trembling. He took her left hand and stroke the palm of it. The scar was now invisible.
She decided to take a plunge. "Patrick, is this your Dark Night of The Soul?"
"Shelagh, I don't know what you mean. Is that some kind of religious image?"
"Yes it is, but the Dark Night of The Soul isn't limited to religious people."
"I don't know what this is..."
They remained silent, facing each other. Perhaps there were things better left behind, Shelagh thought. She didn't really know. Moments passed.
" 'My Gracious Silence' ".* Patrick's voice was oddly high. "Who said that? It was about his wife, wasn't it?"
"Coriolanus."
"Another tormented devil. Oh Shelagh. I can't explain."
"Try. I am not leaving anywhere. Not in anytime soon. This is our kitchen. Our marital home. This is not some...hall of torture."
"No it isn't. But it is not easy ...to describe the hell I saw in the last stages of war. Or the...Northfield. I was in fact a lucky one. I was worn out and...depressed, but at least I hadn't lost all my faculties. There were guys who had hallucinations, paranoid symptoms and nervous tics. It was awful."
"You should have told me. "
"Yes, I should have. Shelagh, I ask you. Once more. To see what is forgivable and unforgivable. If you think that...I have hurt you with deliberate intent... it is not true. I was trying to protect you. I can't say that I succeeded in that. The hurt ... this great...was truly an accident."
"Patrick. I didn't mean to hurt you either." She drew him closer to her. He put his arms hesitantly around her shoulders. Shelagh felt how tense his body was. "But I can't at the moment see what is right and wrong. Or useful. You must give me time. To fully grasp...the forgivable. "
"You think this could be forgivable?" Patrick winced a little. "How odd that sounds". He buried his head into her hair for a moment. "You have had to forgive me so much, starting from that first kiss."
"I thought you a brave man then, Patrick."
He looked up and made her step back a little by pushing her further from him. He watched her with a desperate smile. "Did you? Why?"
"You were brave to respect my vocation."
"Yes. Perhaps it was a bit...courageous."
"I also remember the man who wrote me letters to the sanatorium. A brave gesture..."
"The letters which you didn't answer." He let out a sad little laugh. "I was inclined to think you were deliberate in that. I once lost my...balance for a moment when I realised that you wrote to everyone else but me. It was in the Parish Hall Kitchen. I even nearly broke a tea cup like tonight and started to talk oddly. Trixie was there and thought I was mad. Perhaps I was..."
"Patrick, don't you dare to blame yourself for...loving me. Please don't do that."
"You ask me that? Truly?"
"Yes. I do ask you not to doubt what has transpired between us. All that has happened between us. This...pain included. If this is for worse...then it is. To get better we have to keep living. Until we feel alive again. "
"Oh, to feel alive again..." he sputtered out angrily. Then he sat down by the table. He put his head into his hands. He started to cry. Shelagh sat by him and after a while, drew his head to lean unto her. He didn't resist. There they sat, until it came to an end.
*The dialogue is from "Busman's Honeymoon" by Dorothy L. Sayers, addressing Lord Peter Wimsey's war neurosis. The play Coriolanus by Shakespeare quoted in there.