THE SCORPION AND THE FROG

"What goes around, comes around."

In the end, it doesn't really matter that John Watson says the words, and not his brother.

So this is what it feels like, Mycroft thinks numbly. Of course. He's heard people say that some betrayals are worse than being stabbed in the heart. He'd always thought that particular descriptor demonstrated humanity's tendency towards the dramatic, conjuring that trite phrase. But this agonizing twist, all through him, that pulls and tears and throws his mind into chaos; it doesn't stop. A stiletto to the ventricles would at least be quick.

He wasn't even aware there was a sound recording until now, months after. All the officers had been wired, of course, but this was Sherlock and John and Lestrade in the shadowed ruins of Musgrave, far from where Eurus had been led away. He'd never been meant to know what was said, and wouldn't have, if not for Anthea.

His assistant. Grim-faced, set, with a "You need to know this, sir." Her stock phrase when she knew the contents were gruesome beyond imagining. Her way of warning him. Need to know.

He hasn't yet found a way to ask her how she discovered it.

But she was right.

He needed to know.

Needed to know that despite everything, the fairest man Sherlock knows, the man who has been Sherlock's moral compass for years, thinks that Mycroft deserved Eurus consigning him to her cell.

In John's eyes – and thus, in Sherlock's, later if not sooner – Mycroft is no different from their raping murderess of a sister.

God, but he wishes he was even surprised by it. The pain of the betrayal is not the common shock of how-could-he, but the lesser known agony of how-could-I?

How could I let myself care?

Caring is not an advantage. That does not actually make it a disadvantage. Not in many cases. Even caring set against the recipient's indifference is not necessarily a disadvantage, though it might be a drain on the giver. But caring offered and returned with hatred is worse than a mere disadvantage. It is a victim, baring vulnerable underbelly to a blood-stained predator. It is weakness laying itself out for no other purpose than to be exploited.

It is pain waiting to happen.

Did it never occur to any of them that no one had automatically consigned a seven-year-old to a glass and concrete box with no human contact?

Mycroft hadn't known, but he hadn't assumed. He'd studied the files when the situation became his responsibility, and visited himself. The first facility had been not unlike a home. A gilded cage, certainly, but the gilding had mattered. Eurus had a room of her own, a bed, privacy, everything she asked for, and ample human interaction. Granted, it had been guards and physicians and psychologists, but after a time she'd been allowed to mingle with the other prisoners in that facility. That had been the first mistake. Luckily, only five people had died, over the course of two years and as many riots, eight fires, and countless manipulations.

The Sherrinford facility had still been under construction when Eurus reached puberty, and it became apparent that she needed more secure confinement. The third institution had not been shy about its status as a prison, or coy about its security measures. Nonetheless, in the space of the scant handful of years, Eurus had continued in the same vein, with a disturbing sexual element beginning to play into her actions as her body matured and she discovered new avenues of manipulation that correspondingly opened to her.

The first victims didn't even categorize themselves as such; instead, they were the ones removed and imprisoned for abuse of a minor. Until Eurus got her hands on yet another fellow prisoner.

They found him in pieces. Eurus's willing participation in physical and psychological evaluation after the event was for her education, not theirs. To obtain a baseline for normal response to perceived sexual violation of another, one of her more astute psychiatrists had noted.

That one had requested reassignment soon after, and had been clever enough to seek counselling of her own. She was, thus far, the only person Mycroft could definitively name to have interacted with Eurus and come away relatively unscathed.

But it is more convenient for John to blame Mycroft; someone he knows can be hurt and feel pain. Blaming Eurus is reasonable but unfulfilling, akin to blaming a rattlesnake for its bite. You wouldn't have gotten hurt if you'd just left it alone.

That reasoning ignores Eurus's own volition.

After being at her mercy, Mycroft wouldn't think that Eurus's deliberation would be an easy thing to forget. But he is apparently wrong. Even after being hauled up from the well in which Eurus had chained him, kept company by the bones of the little boy she'd put there when she was even younger than Victor Trevor had been, somehow Mycroft is the villain.

He is shaking inside, though the hands clamped around the arms of his chair are perfectly steady. He wants to vomit, but his stomach is rock-solid.

That's the shape of her newest manipulation, at least on the surface. The victim. A role remarkably trite for her, in the vein of countless individuals perceived by society as smaller, weaker, or disadvantaged, and who learn to play off the stereotype straight into the system's politically-correct knee-jerk rejection of it. And it will work, because none of them care to know her history, or the truth.

Because the truth is that Eurus had earned every security measure, every day without human contact, every year without sunshine or fresh air. She'd bought her imprisonment with other people's blood, shed both dispassionately and voraciously.

Mycroft has killed. He despises legwork for a reason. He can handle a gun, from the modern to the antique, and is skilled with a blade. But he can at least say that no one who died at his hands did so for any reason other than his self-defense. Despite what his brother thinks, he doesn't actually make people disappear.

Eurus killed because she wanted to. Life means nothing to her. The sanctity of an individual's body and mind were concepts that she acknowledged only as theories, waiting to be tested.

She wasn't taking any type of revenge on him, by locking him in her former cell, despite what Watson assumed. She was simply storing her next test subject for future use, in the place she thought him least likely to escape on his own. However long he might have languished there meant nothing to her.

His whereabouts clearly meant little to Sherlock or Watson, caught up as they were with Eurus's experiment at Musgrave.

It's a good thing that Mycroft learned early on to save himself, because no one was ever coming to his rescue. Even the inception of this case had been about Sherlock obtaining information, not about actually helping Mycroft. He'd never wanted to be saved; but he would have liked not to always be so utterly alone.

Sherlock had never been what anyone would call reliable. But Mycroft used to think – used to hope – that in extremis, Sherlock might be counted on. It had never been a constant, but the variable had at least been present in his calculations.

He would have to remove that variable entirely going forward.

Especially in light of the visits, and the violins.

And now this.

He'd been spared Sherlock's automatic, vitriolic agreement, but the quiet contemplation in the wake of Watson's statement was worse. That was Sherlock, assessing the factors and coming to a decision. And utter silence on the topic, for months. Never a hint that Sherlock had known.

Now Mycroft really wished he could throw up.

"What are you still doing here? Shouldn't you be off getting me a pardon or something, like a good big brother?"

He'd spent his life shielding Sherlock from the consequences of his foolishness. Because Sherlock was extraordinary, his foolishness was so far beyond the normal that the consequences likely would have killed him in the majority of extrapolations Mycroft had run. So Mycroft had stepped in.

He hated that he wished now that he hadn't.

He'd had to. Of course he had to. He'd loved Sherlock, and Sherlock had been killing himself with drugs, his brilliant mind laying waste to his body and all around him.

Mycroft is the oldest. Mycroft has been corralling his siblings for their entire lives.

Mycroft is tired of being sacrificed for the sake of preserving two people who would, actively or out of carelessness, see him dead. Sherlock at least wouldn't vivisect him, but there's little more Mycroft feels he could say in his brother's favor.

"Go away, Mycroft."

Eurus is Sherlock's new side project, and he is no more immune to her manipulations than he's ever been. Mummy and Father are barely accepting of the upper limit restriction on visits, constantly clamoring to spend time with the daughter who had been lost to them, and uncaring of Eurus's flat disregard for their presences. They do, however, approve of the duets.

He knows, deeper than reason, deeper than logic, deeper than the hollows of his bones, that nothing good will come of this. But he doesn't know what.

He can't see what is to come, but that's only because the shape of it is obscured by tears.