A/N: the only fucking thing that could have saved this stupid scene for me

When Eurus asks him to "play you," his stomach drains. He looks at her with questioning eyes, uncertain eyes, waiting for her to elaborate or clarify; she stares back and says nothing.

"Me?" Sherlock asks, parroting back at her, feeling more stupid than he ever has. She looks at him with the self explanatory disdain that he has felt towards so many other people, and snaps in a breath, "Don't be so willfully ignorant. You."

He doesn't know what she means.

So it surprises him when Waltz for John and Mary leak from his violin, lovely and soft and torturously slow, laced with desire - he was the only person I ever wrote music for, Sherlock thinks - and by the fifth note of the waltz, he understands.

This song is every drop of love he ever had, more love than he thought he was capable of possessing. Every draw of the bow across the strings is another layer of his self-sacrifice, his adoration. Sherlock still remembers holding John's hand in 221B, twelve days before his wedding night, arm on his shoulder, stepping closer and stepping apart in the same beat. Never too close. Never close enough for John to feel guilty. Never close enough for John to know. 

Unlike John, but very much like everyone else, it seems, Eurus knows. He shuts his eyes tightly so he can't see her revel in it, to marvel at the sight. From what she must have gathered about his personality from the night they walked around London, she must know that she has hit a sore spot.

This song was his, and he gave it to Mary - God, it makes his heart ache.

"Have you had sex?" she asks, fascinated. She's reassured in the answer but Sherlock resists giving it to her.

He replies, "Why do you ask?" like he doesn't know, like it's not written all over his face. It's not a skillful way to avoid the question but at this point he's blundering. Eurus has torn his defenses apart in a matter of two seconds and five words and for a self-indulgent moment he wonders what John would think if he were here.

"The music. I've had sex."

"How?" Sherlock immediately responds, grasping for a way out of his self-examination - he's already looked at the way he loves John Watson under a magnifying glass too many times, and he's trying not to subject himself to that now. He continues playing as she responds, rapid-fire, cold.

"One of the nurses got careless; I liked it; messy, though. People are so breakable."

He agrees but not aloud, and then allows himself to truly process the sentence. "I take it he didn't consent."

Eurus cracks a smile, and there's humor in it, real humor. She finds this fascinating. For her, this crucifixion, this vivisection, is a delight. She is cutting him open and reaching inside and looking closely at his heart, gushing with blood, and for the first time in his life, Sherlock feels like the normal one. He has never done this. He has never tortured someone in this way. It holds no interest to him.

But Eurus... her smile is genuine, self-congratulatory. "He?" she presses.

Sherlock knows what she wants him to reply, but it won't push through his teeth. Even as he plays on, he is silent. 

"The music," she laments, once again. "Waltz, no?"

"It's a waltz," Sherlock concedes, although bitterly.

"This is you, Sherlock?" she thinks aloud. "This pathetic ballad?"

Sherlock remains silent, but the vibrato in the piece shifts from stiff to chaotic.

"You haven't had sex," she remarks, a smile still leering over Sherlock, "and yet."

He wants her to stop speaking. She's too close.

"The assumption is that I had sex with a man. You know fully well that nurses are statistically more likely to be women. You never cease to be unconventional, do you? Never boring. Oh, this is fun. Does he know?"

Sherlock shakes his head, as if to clear out his ears. "Does... does who know what?"

"Oh," she laughs gleefully, "you know that I know, and still!" Her expression becomes almost incredulous. "It's written on your face! This isn't sex, this isn't pleasure; no, it's pain, it's love, it's self-destruction, it's you, it's all you, Sherlock. I'm fascinated."

"Fascinated?" Sherlock is shaking now. No one has laid it out in such point-blank terms before, and as he hears it out of someone's mouth, it hurts impossibly more. The hand that refines the pitch of the notes quivers, and the tone suddenly gives out. Horrified at himself, he struggles to regain composure.

Eurus ignores him and asks another question, and though it doesn't relate to the conversation directly, it's far worse, more condemning than anything she could have said in reply. "Is that vibrato? Or is that your hand shaking?"

Sherlock stops playing mid-note. His chest is heaving. She knows and everyone else knows and John doesn't but he wishes that he did, if only to end his featureless agony, his nebulous torture. Sherlock never thought love would be like this.

Again, she repeats, "Does he know?"

"That I love him?" Sherlock whispers into himself. He's not saying it to Eurus, but she hears him.

"He must." She's not grinning, anymore. "It's pathetically obvious."

The most bitter shadow flickers across Sherlock's face. "I know," he eventually allows, voice impossibly small; dead steady for fear of wavering.

Seconds of thankless silence pass. Eurus, now satisfied with the course of the conversation, curiosity sated, quirks her lips in a smile as they both realize exactly how she quantifiably has won.