I would recommend reading 'Engraving' first. It isn't necessary. But there is a line that calls back to that.

So... I really don't know what to make of this. I honestly don't. Sherlock is weird. It might end up being one those things that only makes sense to the author...

If you haven't seen the 'i love you scene' i strongly recommend you watch it... But this is like a combo between the mind palace scene of HLV or the crazy best man speech during TSoT. That's why I'm not sure about how much it makes sense.

Disclaimer: I don't own any of the characters or the scenes referenced to. They belong to ACD & BBC Sherlock. This is just my interpretation.

Technicalities

Sentiment demanded answers. Vindication. Justification. It had consequences.

Sentiment, a chemical defect found on the losing side…

And he dripped of it.

Brother. Goddaughter. "Best"…. Best friend. Friends, as in the plural. And now… Sister. Secret sister. Even in his mind it sounded dubious.

They lost, the moment they came to the island. They lost. Transparent in hindsight.

If he was smarter, maybe he wouldn't have come. They wouldn't have joined.

But he'd be an idiot if they hadn't investigated. After all, she started the game. And he needed to finish it.

Defect indeed, sentiment. It blinded you to the truth.

Redbeard.

After all these years, surely he would have figured it out. But he hadn't. And Eurus wanted to know why. Sentiment, after all. She didn't understand it. Couldn't comprehend it. She understood the chemistry. The science. The cause and the effect. But couldn't understand why it influenced action.

It was an experiment. For every action, there is a reaction. That's why the trials. The trials was to see how sentiment ruled your heart. His heart. How it influenced your priorities. His priorities. She already knew the outcome. She just wanted to witness the grit in the instrument. To watch the process unfold. To watch him unfold.

That's why John.

That's why Mycroft.

To contrast the process between those unknown to him to those he knew well.

It was a thin line he balanced. Between the cold, hearted machine to being human. But lately, its been more of the latter.

Eurus must have been watching for some time. She must have been. Just like Magnussen knew the pressure points, the weaknesses, she knew, but she was far more clever. She knew the vulnerabilities he had acquired. Unknowingly, he set the game in motion. Five years ago she started the clock. She finally had the leverage.

Five years since John Waston had joined the game.

He could detach himself. Remove himself from the equation. Divorce himself from feelings. But he couldn't fool anyone, even himself, where those closest to him are concerned. Mary was evidence of that.

But to save their lives. He could be the machine. Even if it was all for appearances.

Maybe he had been wrong. Maybe it hadn't been John who started this.

The moment he saw it,... this wasn't a game at all.

'I love you'

The sensation was immediate. The flush he felt throughout his body. The surge of catecholamines that swept within his vessels. Sympathetic system overriding everything he worked to control.

Elevated heart rate. Dilated pupils. Sudden perspiration. The way his breath hitched for a second. As if he couldn't get enough air.

His body betrayed him. The chemicals had taken affect and he couldn't hide it. It was all too… physical. Observable.

…you'd better break it off now and save yourself the pain…

He'd told himself this once. Long ago. He couldn't remember the circumstance. No doubt he ignored it. Disregarded the fact that the thought had even occurred. Because it didn't matter. What mattered was the case. He needed results and she could get it to him. Easily. Efficiently.

A remarkable woman of rare perception.

Yet, it was sentimental. Pushing those thoughts aside. Working to ignore it. Work took effort. If she hadn't mattered, the thoughts wouldn't have occurred.

But it was natural.

…the one person that mattered the most…

He attempted, on rare occasions, to delete them. But like all emotions, you couldn't delete it. Emotions made experiences palatable. Made them into memories that stayed in the brain. The more powerful the emotional catharsis, the more likely it would remain.

Permanent.

He couldn't remember where or when it started. Years of suppressing an outward physical expression to any experience stunted the association. But it was there.

You've always counted and I've always trusted you.

He knew because of his mind palace. Behind lock and key. But she always found a way out. In the halls. In the rooms. She pervaded throughout.

Her perception a rarity.

What's going to kill you?

Analyzing any situation, this question always came to the forefront. But now it seemed it was reversed. Seeing her, clear as day in his mind, in the hallway, he asked the Molly that stood before him in his mind, what's going to kill you? But she doesn't respond. She always had something to say. Working through deductions, she was always on hand, stating the obvious before he even thought it.

But not now.

At the present, Molly is on the screen. She is home. Making tea. And ignoring his phone call.

Thump-thump!

The sound resonates and he turns away from Molly, looking down the hallway but he can't pinpoint its origin. Looking back to her, but she's gone.

Thump-thump!

Surely the others heard it. The thump that was suddenly so loud in his ears. He doesn't dare look back to them though. He doesn't need them to see his face.

The screen. A timer. A challenge.

Thump-thump!

The sound is loud. Its bounding through the halls. Each door he opens, each room is empty. He can't find it. He can't find its source.

Its a difficult thing. Remaining impassive.

"I'm not an experiment, Sherlock." He can hear her dejected tone.

"No, I know you're not an experiment. You're my friend. We're friends, but.."

Thump-thump! Thump-thump!

Lie. He knows its a lie.

The timer was ticking down. The thuds were bounding loud, he could feel it inside.

"If its true, just say it anyway." He hears himself say. He tries to be cold. Tries to remain impassive. But its a difficult thing.

Molly is in the hallway again. Staring at him. She is silent.

He can hear his voice echo: If its true, just say it anyway.

Say it anyway.

Say it.

Say it.

The timer counts. Each second threatening.

Tick-tock, tick-tock.

Thump-thump!

Say it.

Love is a vicious motivator. You'll do anything.

He puts words to what he's been too stubborn to say, too stubborn to understand. To stubborn to acknowledge.

"Molly… Molly, please."

You'll do anything. Even beg.

Please.

She hesitates.

Please.

Thump-thump!

It'll be too late before she even utters the words.

Please.

Breathing is difficult. Its rapid. The air comes, but its minimal. Some ventilates his lungs. Perfuses through the cells into his blood. Hemoglobin captures the oxygen. Running through his body. To his brain.

But he can't get enough. He's lightheaded. His fingers tingle. His legs feel numb. Moving doesn't help. Stepping from one leg to the other.

Molly Hooper is there, in his mind. But she is silent. Staring.

Please.

And then it comes, the release code. Its soft, but he hears it.

Breathing out air that he doesn't have in him. A sigh of relief. His chest tight. Eyes warm. It stings as he closes them. Rubbing them with the palm of his hands. He can feel the metal in his hand. Its warm and clammy.

Thump-thump!

He could be the machine. Even if it was all for appearances.

"I won. I won… I saved Molly Hooper."

"Saved her? From what? There are no explosives in her little house. Why would I be so clumsy?" Eurus mocks.

But he never wins. Not when it comes to her. Not when it comes to Molly.

I am sorry. Forgive me.

Everything is always more than he expects. More emotion than he was planning. More he has to answer for that he isn't prepared to do.

Thump-thump!

"You didn't win. You lost. Look what you did to her. Look what you did to yourself."

It all had gone by so quickly. Three minutes that seemed too fast. Each second, a second closer to losing something he barely understood. Everything moved so quickly. Too quick for him to realize it was all a ruse.

"All those complicated little emotions. I lost count. Emotional context, Sherlock. It destroys you every time."

This is your heart and you should never let it rule your head.

It feels as if he's stopped breathing. He doesn't even try.

He could be the machine. Even if it was all for appearances.

Thump-thump!

But before he realizes, he's across the room. Grasping the coffin lid. Carrying it over to cover the empty box.

He tries to stop himself. Responding is acknowledging. Reacting is accepting. It provides the credibility to Eurus' statements. Its as good as a confession.

He could be the machine. He needed to be the machine. Internalize it all and move forward.

Thump-thump!

But he's shaking. He can feel it in his hands. Sees it as he brings his left hand over the engraving. Hovering, but not touching.

'I love you'

…is this one of your stupid games?

It wasn't a game at all.

The words engraved on a coffin is chosen by the loved one of the deceased. That is what Eurus' is implying.

His beloved. The person he loves. It was never about who loves him. But who he loves.

Eurus wanted to show this. In this game that wasn't a game. To reveal a truth that wasn't tangible but yet still observable. An experiment. The trials, to see how sentiment ruled his heart. How it influenced his priorities. She knew the outcome. She just wanted to watch him unfold.

He wanted to walk away. Leave the coffin to rest. He didn't want to reveal anymore. He didn't want to feel anymore.

But she was still there. Standing there in his mind. In the hallway. Not speaking. Just staring.

Look at what you did to her.

You always say such horrible things. Every time. Always. Always.

Look at what you did to yourself.

He was still shaking. His pulse still elevated. His breathing still increased. And as much as he convinced himself she was safe for the moment. Safe at the present. The feeling wouldn't abate.

I hope you'll be very happy, Molly Hooper. You deserve it.

But she wasn't. Was she?

Why are you doing this to me? Why are you making fun of me?

You know why.

You bastard.

Thump-thump!

He wanted it to stop. It was there and it was deafening. He could feel it in his chest. The heart he refused to believe he had.

Thump-thump!

Molly still stood in his mind. She was quiet. She didn't move. She only stared.

Thump-thump! Thump-thump! Thump-thump!

It was so strong. The beating. It was so loud.

I'll burn the heart out of you.

Looking to Molly. She hadn't moved an inch.

He didn't want to hear the answer. He knew the answer, but he didn't need it verbalized. He knew what it would do. He knew what he would do. The coffin still sat there. Untouched. Unneeded. Unnecessary. Yet he couldn't stop the thought. He'd beat it to a pulp. He'd feel the splinter of wood in his hands. But he wouldn't care. He'd roar into oblivion because he didn't need it to be true.

Molly was always there for him. And he couldn't reciprocate.

He tried again, what's going to kill you?

And this time, she answered.

You.