Idk how much sense this will be... This is Mycroft's perspective of Sherlock during the coffin scene in TFP.
P.S. I'm also on ao3 with the same username.
Disclaimer: I do not own these character or the scenes referenced to. They belong to ACD & BBC Sherlock. This is just my interpretation.
Sherlock was always quick to jump the gun. Ready to spout deductions in rapid fire succession at the fault of overlooking the obvious.
He always missed something.
Unless you had a mind like Sherlock's. You didn't understand. He was brilliant, to be sure. He was clever.
But Sherlock's mind was jumble of data. More muddled than most could see. Most only saw the impressive nature at which he could arrive at a conclusion. Which was more often right. But there was always something he missed.
Eurus knew this. She knew then. She knew now.
Only she had the ability to see it all. She had the foresight to know what would happen. She could arrange the board and anticipate every outcome. She could execute a plan, even when she knew the result.
And she always knew.
She just didn't understand, why.
Emotion. She could define it. But she couldn't feel it. Appreciate, maybe. But not experience.
Mycroft watched as Sherlock analyzed the coffin. Pressed for time. He verbalized fact after fact. Removed from the situation but still in the moment.
Height.
Gender.
Class.
Practicality.
Sherlock could tell you every minuscule detail about a person until he was blue in the face. But he would still miss the primary question.
Whose coffin?
Mrs. Hudson was correct. Sherlock was more emotional. Blindly driven by the desire to understand. A pride that welled inside when he finally did. It clouded his thinking. Admittedly, more often an asset than a fault.
But, here. Now. Even Sherlock should have noticed the coffin that sat without a lid. A lid carefully set aside. The answer he seeked, concealed but still accessible. Right in front of his eyes.
Mycroft never understood Eurus' fascination with Sherlock. Even as children. She would be bored whenever she spoke to Mycroft. But not Sherlock. She was curious about him. Its why they were here. Why they were all here.
This is what Mycroft overlooked. All these years, Eurus never uttered Sherlock's name. But all these years, she was planning. The Consulting Criminal. Moriarity's interest, nearing obsession with Sherlock. As it turned out, Moriarity, a mere pawn in the grand scheme of things.
Looking at the engraving on the coffin. A dawn of realization came over Mycroft.
Sentiment, a chemical defect found on the losing side.
He often told Sherlock this when they were children. Sentiment evoked emotion. Sherlock was always quick to anger, sadness, fear… Joy.
But after Redbeard, there was nothing Mycroft could do to bring back the joy. The other emotions always at the forefront. It was easier to condition him. To suppress it. Taunting him till he ignored it.
Reason and logic, the answer. But, still Sherlock struggled there.
Which made Sherlock easy to manipulate. Sentiment always got the best of him. In the midst of strong emotional currents, you could mislead him. You can make him overlook things. Make him miss things.
'I love you.'
Naturally. The words engraved on a coffin would be chosen by a loved one of the deceased. A last piece of sentimental expression to the person lost.
Not generally chosen by the deceased.
Balance of probability would claim the former.
Sherlock's proclivity to emotional outbursts was well founded. But Sherlock was stubborn where sentiment was concerned. Stubborn to recognize it. Stubborn to acknowledge it.
Whose coffin?
Someone Sherlock loved.
This train of thought was foreign. Unfounded. Mycroft never thought he'd see the day. And he'd be the last to admit he didn't see this coming.
Mycroft, confident this was a revelation Sherlock had not discovered. Had not even postulated.
Yet, Eurus saw it. Of course she did. She set the game. She laid the pieces.
She was waiting for the play.
'I love you.'
Sentiment. Mycroft knew Sherlock's limits. This sort of revelation wouldn't have come for years.
But here. Now. There was only so much Sherlock could manage. Where life and death straddled a seemingly nonexistent line. Sherlock wouldn't cope.
So he switched it. The emotions were high. Palpable. He could easily direct Sherlock down a different train of thought.
"…we can just look at the name on the lid." Mycroft started.
It was clear on Sherlock's face as soon as he saw it. Mycroft just wasn't sure which path he'd take.
"So, its for somebody who loves somebody." John thought aloud.
Adjusting the choice of words, "It's for somebody who loves Sherlock. So who loves you? I'm assuming its not a long list."
Mycroft looked on. Praying this would take.
"Molly."
Molly? Molly Hooper. Doctor Molly Hooper.
The Molly Hooper that helped with the fall. Molly Hooper, that he kept tabs on but didn't look to with as much scrutiny as John Watson. Molly Hooper, who Sherlock only mentioned a handful of times.
Sherlock had hid it well.
Eurus had more time beyond these walls than they ever imagined. She saw this, that no one else noticed. It was evident. She planned all of this for Sherlock after all.
She anticipated the desperation. The guilt. The anxiety. The stress. The realization that would arise under pressure.
Sherlock's behavior unlike anything he'd ever seen. Sherlock's voice unlike he'd ever heard him.
Eurus saw everything Sherlock tried to ignore. And made it clear for them to see.
The emotion was real.
Mycroft hadn't expected this.
"In your own time." But Eurus did.
Silence.
What more could they do. This task was done. Molly was physically unharmed. And based off the past two challenges, that was all they could ask for.
Slowly, Mycroft made to move to the next room. He knew it would come, but he was hoping it wouldn't.
Mycroft watched as his little brother stayed back. Pacing the room. Ignoring them both.
Delicately, Sherlock's hand hovered over the engraving. Three small words. But the depth in meaning…
The words engraved on a coffin would be chosen by the loved one of the deceased. That was Eurus' implication and Sherlock finally registered this.
With each strike, the understanding grew. The despair. The guilt. The loss.
With each scream, Sherlock recognized it for what it was.
He always missed something. And this was something he had missed for years.