Horror fills his steely grey eyes as he looks down at his angry, furious best friend, and his other, dear friend- dead, with blood forming a large, ugly patch on her abdomen, mocking the detective of how he had failed his vow.
How could he have failed to protect Mary?
He had vowed to them- vowed to them- on their wedding that nothing would happen to them, not on his watch.
...
His first evening following her death is the hardest. He is numb with shock over the affair- medics pronounced her dead at the scene, and took her to the morgue at Bart's, leaving John to catch a cab in stony fury, and Sherlock to walk home, silently comprehending on Mary's death, and John's reaction.
Sherlock has a sickening feeling that poor, sweet Molly may have to see her dead friend on a slab there, leaving her to the stomach-turning realisation that Mary is leaving mourning friends, a furious and heartbroken husband, and an oblivious infant daughter.
Mrs Hudson cannot stop crying when she hears the news, though she tries to be brave and offers her tenant tea.
He declines politely for a change, feeling that he had let Mary down- scratch that, he let everyone down.
It hurts him just as much, if not more, when he 'died'. John cuts himself off from his friend: calls go unanswered, knocks on the door held no significance; his voice was echoing in Sherlock's mind palace.
Feeling unable to stop beating himself up about his failure to protect Mary- his friend, he decides to instead bury himself in his experiments and cases.
"Work is the best antidote to sorrow," becomes his mantra through his grief and failure as a guardian, as a detective, and as a friend.
Afterwards, when he feels a headache forming, he decides to compose a tragic, soft ballad in memory of Mary Watson (nee Morstan). He settles on the sofa with his prized Stradivarius, and his fingers begin to glide.
He allows his feelings to guide his bow, and the results pour out from within its strings, each note more heart-rending and beautiful than the last, until...blackness curtains his vision.
...
"I can still surprise you..." Vivian Norbury hisses treacherously.
That dreaded signal that his life- as well as others- goes into a downward spiral.
Sherlock can't even breathe- he watches helplessly as Mary's death replays itself in his nightmare, surrounded by blue, transparent curtains and a bored audience of sharks- and then John is suddenly punching, kicking and screaming obscenities at the sleuth, yelling at the detective, blaming him for the death, and calling him a failure.
"You made a bloody vow Sherlock!" The doctor roars, and kicks his friend in the abdomen. Hard.
Sherlock winces in pain, and he weakly wriggles away, like a pathetic earthworm trying to avoid the savage talons of the early morning crow.
"John... forgives me. I..."
"You bloody arse! I thought I found true happiness at last, but you destroyed it! You're a selfish man, Sherlock Holmes, not to mention a bloody idiotic failure!"
'Failure...failure...failure...'
...
"John, please!" Sherlock gasps, and his eyes shoot wide open in alarm.
But the appeal is to an empty flat.
"It was just an irrational dream, Sherlock." The consulting detective reassures himself. Noticing his violin snuggled close, he shifts it to an empty space on the sofa, and rises, before pacing round the room.
"Sherlock, what's wrong, dear? I heard you downstairs from my flat."
Standing in the doorway of the living room, in her favourite purple cardigan over her nightie, Mrs Hudson looks at him worriedly, concern evident in her kind, soft brown eyes. "I came earlier to see you needed anything, but you had fallen asleep on the sofa."
"It's nothing, Mrs Hudson," Replies Sherlock in annoyance, ruffling his curls with his long, ivory fingers. "I apologise for disturbing you."
Even so, he is badly shaken, and he feels tears pricking at his eyes, so he avoids his landlady's gaze in order to keep his feelings hidden, but it took more than that to fool her.
"Now, Sherlock, you should really open up," She chides gently. "I know you're not fond of talking, but you should get help. Hasn't John called?"
"John wants nothing to do with me, Mrs Hudson."
...
Sherlock waits until Mrs Hudson retreats before he goes to sort out his newest experiment. But the nightmare, no matter how irrational it was to him, kept playing in his mind. He didn't get it- only half of it happened. Why was his brain being so difficult?
On hearing a series of clinking sounds behind him, the detective almost drops a test tube of sulphuric acid.
"Sherlock, come and have some tea, dear."
As much as he hates to admit this, tea does sound nice right now. And he's not in his best friend's favour anymore, so he might at least try to be civil.
So he lets her pour him a cup of tea, and she sits attentively, taking his hand in her own withered one and rubbing gentle circles on it with her thumb.
Suddenly, Sherlock feels a compulsive urge to...say something, and he does.
"It's my fault, Mrs Hudson. I got her killed."
"What do you mean, love?"
Taking a deep breath, he steels himself for the one thing he can't handle: emotions. Specifically, guilt.
"I...I went too far with my deductions. I said more than I should have. Vivian...she...she..."
Mrs Hudson continues rubbing his hand, and he forces himself to calm down a little.
"She attempted to shoot me, Mrs Hudson. She wanted me to die- but Mary...she...took..."
He couldn't finish- he literally cannot- but it isn't needed.
"Oh Sherlock..." She gathers him up into an embrace.
"John was right- I'm a bloody failure..."
"No, Sherlock, you're not." Mrs Hudson says firmly, pulling back from her hug to regard her favourite tenant. "Mary didn't save you to allow you to think you failed her and John. She saved you because you're part of our family. You were a big part of her life, Sherlock, and she loved you- as both a friend and a brother."
"But John...he said...I...I failed...to honour my vow..." Oh dear God, he's crying, he realises with disgust. But he can't help it- he's traumatised by the whole incident, and although a number of people have died because of him, Mary Watson's death was the biggest stain of his conscience. Mycroft, as much as he hated to admit it, had been right- he hadn't been able to protect Mary forever.
"I know you made a vow, Sherlock, but sometimes, it's just not meant to be." She says, looking up at him with a tearful smile. "I made vows to my husband, and he was"-
"Bloody awful?" Sherlock deduces her next words.
"Oh God yes." Mrs Hudson agrees, before her eyes turn solemn. "Besides, Sherlock, you vowed to protect Mary, John and little Rosie. Mary may be gone, but you can still protect them. Be their guardian angel, if you like."
"I don't believe in guardian angels, Mrs Hudson."
"Please, Sherlock. I don't want you to lose faith in yourself. Look after John and Rosie, but remember to grieve for Mary, and honour sacrifice for you, not blame yourself for her death."
She pulls Sherlock in for another embrace and the consulting sleuth returns it this time, feeling tears seep out of his eyes and pool onto Mrs Hudson's cardigan.
The two do not speak for a long, long time, but they don't need to. The fact they had each other to support them through their grief was enough.
And Sherlock's nightmares settled too, but he asked Mrs Hudson for the phone book the next morning.
He needed professional help.