Sherlock's step faltered; despite the fact that he'd been prepared to hear the worst, he hadn't quite expected this.

'Seven percent! Oh, Marie.' Sherlock thought in horror, while Eurus continued: "It was Jim's idea at first, and I liked it, but didn't think I really needed it. Good thing I kept some prepared anyway."

Sherlock almost couldn't speak, he was so staggered; but his mind returned sharply as Eurus said: "But enough of that: I'm giving you one last chance, Sherlock."

Sherlock opened his mouth, but Eurus wasn't done speaking: "If you win this round, I'll give you back Dr. Watson and Victoire; you will be able to speak with the little girl; and I will tell you where Mycroft is so he can help you save her."

Sherlock waited warily for Eurus to name her terms, waiting for the catch, and she did just as Sherlock noticed a blank screen on the far side of the entry hall, near the staircase.

"Find Redbeard, Sherlock."

The screen came to life, showing Eurus once more but now she was in some dark room with only enough light to light up her face as she said seriously: "I'm letting the water in now. You don't want to lose your wife again, or want me to drown another one of your pets; do you?"

Sherlock stared at Eurus in mute horror as she smiled: "At long last, Sherlock Holmes, it's time to solve the Musgrave ritual."

Sherlock shook his head slightly, stumbling back from the screen; it was impossible, not even Mycroft had managed to figure Eurus's problem, and he had had years to think about it. How could Sherlock solve it now? How could he save those he loved most if he couldn't?

As Sherlock reeled, Eurus chirped: "Your very first case! And the final problem. Oh!"

She gasped lightly in what appeared to be genuine excitement and anticipation, before she smiled slightly at Sherlock as she whispered before she disappeared from the screen once more: "Bye-bye."

"Sherlock?" John called in alarm as water started to pour down into the well, coming down almost like someone had turned a shower on above the well opening.

He dropped the bones he'd been showing Marie, while Marie also shed away from the falling water with a moan as, over their earpieces, Eurus sang: "I that am lost, oh who will find me. Deep down below-"

"Sherlock!" John called sharply, pressing his hand to his earpiece as he tried to get in touch with his friend as Marie moaned again while Eurus continued to sing.

"The old beech tree?"

Inside Musgrave Hall, Sherlock walked slowly across the hallway and opened the door to another room, while Eurus sang ominously in his ear: "Help succour me now."

"Marie. John." Sherlock gasped at what he saw inside the room, while Eurus just carried on singing.

"The East winds blow."

Sherlock dropped his lantern hurriedly on the ground by the door, while he called: "Marie. John!"

But apparently Eurus had cut their communications for the moment, only letting them hear her terrifyingly emotionless singing.

Sherlock could only stare helplessly at the large screen attached to the far side of the wall, going to stand directly in front of it as he watched John huddle down inside the well, trying to shield Marie from the water pouring down into the well.

"Sixteen by six, brother."

"John, can you hear me?" Sherlock shouted into his earpiece. "Marie? MARIE!"

Marie appeared worse than before, her head lolling almost lifelessly on her shoulder as she leant back heavily against the stone well walls. She didn't even really seem to notice the water or John right in front of her, and Sherlock gripped his hands in tight fists as he stared worriedly at the screen where he could see John continuously tapping Marie, as though urging her to remain conscious.

"And under we go…"

Sherlock heard a faint scream in the background of Eurus's singing; the little girl again.

But before he could call out to her, the communication line switched to John and Marie, and Sherlock pushed his earpiece in further so he could hear better as he heard John call faintly against Eurus's singing: "Sherlock?!"

"Be not afraid…"

"John!" Sherlock called back to John, who shouted over the sound of the water rushing in and Eurus's singing: "Yeah, it's flooding. The well is flooding!"

"To walk in the shade."

John glanced down where the water was rising up to his waist, before he reached over and grabbed Marie, hauling her up to her feet before she could drown from her place seated against the well wall.

"Save on, save all."

Marie stumbled, clearly not in control of her own body, and Sherlock watched anxiously as he called: "Marie, try as long as possible not to drown. That goes for you as well, John."

"Come, try."

"What?" John asked, pushing his own earpiece deeper into his ear as he struggled to hear Sherlock over the sound of the water and Eurus's singing.

Sherlock sighed, both in exasperation and in agitation as he called back: "I'm going to find you both; I am finding you!"

"Well, hurry up, please, because I don't have long!" John shouted back, pressing his hand against his earpiece as he glanced between the rising water and Marie. "And I think Marie has even less time than I do!"

Sherlock shifted anxiously, rubbing his hand down his face worriedly as he struggled to think. Leave the room and risk losing sight of John and Marie when he didn't even have a clue where to go? And how, how to solve Eurus's riddle?

"Who now will find him?"

He started as the little girl screamed in his ear again, the girl crying in panic: "It's leaning over, the whole plane!"

Sherlock dithered, unable to move as the fear slowly began to creep up like a cold paralysis all over his body.

Inside the well, John handed the bones he'd found to Marie, who took them absently, before he turned and felt along the rocks, trying to see if there was any way to climb out. He lifted his leg as high as he could, trying to pull himself onto a higher perch, but the chain on his foot caught and pulled him back down.

John fell with a splash back inside the well, almost hitting Marie as he did – not that she really seemed to notice as she spaced out at apparently nothing, the drugs too strong on her inexperienced body.

"Lost forever, nine by nineteen."

"Eurus!" Sherlock called desperately as he turned and stalked out of the room with the screen of John and Marie, walking out into the hall while his sister carried on singing.

"You said the answer's in the song, but I went through the song." Sherlock pleaded as he paced in the entry hall before the first screen that was now blank. "Line by line all those years ago; and I found nothing. I couldn't find anything."

Sherlock stared at the empty screen, begging silently for Eurus to give him some form of a clue so that he could save his wife and best friend from Redbeard's fate as he rambled frantically: "And there-there was a beech tree in the grounds and I dug."

Sherlock's voice cracked as he continued feverishly: "I dug and dug and dug and dug. Sixteen feet by six; sixteen yards; sixteen metres - and I found nothing. No-one."

Sherlock stared at the screen pleadingly, only realizing that Eurus had stopped singing when it was deathly quiet for a beat. Then-

"Sherlock?" John called over the earpiece, and Marie's voice mumbled dazedly: "Sherlock?"

Sherlock closed his eyes at her voice – her wonderful yet terrible voice, sounding so weak and tired and lost – before he snapped them open once more as Eurus reappeared on the screen, saying: "It was a clever little puzzle, wasn't it?"

Her tone went deadly as she asked: "So why couldn't you work it out, Sherlock?"

Sherlock raised his hands, pressing them to his mouth as he tried to think, when John called urgently over the comms: Sherlock? There's something you need to know."

Sherlock lowered his hands, breathing heavily and looking around wildly as he tried to figure out the riddle.

"Emotional context." Eurus suddenly piped up, and Sherlock glanced at her. "And he~re it comes."

Sherlock frowned, while John continued to call anxiously: "Sherlock? The bones I found…"

Sherlock turned from Eurus's screen, moving to walk into another room down the hallway where there was another screen hanging from the wall, as he said to John impatiently: "Yes? They're dogs' bones. That's Redbeard."

"Mycroft's been lying to you." John informed him, his voice trembling slightly. "To all of us. Marie... just pointed it out to me; she figured it out with one touch, and she's right."

Sherlock frowned in confusion, when John dropped the bomb.

"They're not dogs' bones."

Sherlock blinked, the information unable to sink in due to the shock that paralyzed his entire being, as Eurus asked: "Remember Daddy's allergy? What was he allergic to?"

Sherlock could only stare at the screen as Eurus taunted: "What would he never let you have all those times you begged? Well, he'd never let you have a dog."

Sherlock jerked as, in his mind, a dog barked. Screwing his eyes shut, Sherlock let the memories he'd suppressed for years come flooding back, the memories of the family visit to the beach coming in flashbacks as Eurus continued to speak.

"What a funny little memory, Sherlock."

Sherlock's breathing started to become laboured, coming harsher as his throat constricted. The dog in his memories at the beach, his best friend from his childhood, and his fellow 'pirate'…

"You were upset," Eurus went on, "so you told yourself a better story."

Sherlock staggered back. No… it couldn't be… The bloodhound Sherlock had always recalled so vividly, with the reddish-purple bandana tied around its neck, was actually…

"But we never had a dog." Eurus finished darkly, emphasizing each word, just as Sherlock recalled the true scene from his childhood.

Sherlock running across the beach as a child, splashing water as he played pirate with his plastic sword, while a little ginger-haired boy around his age, dressed in a plaid shirt and with a reddish-purple bandana around his neck, ran after him with his own plastic sword and a toy eyepatch over his right eye.

Inside the well, John grimly picked up the human skull that Marie had told him would likely be in a corner of the well, lodged where the water swirled around. She had immediately figured out the bones that John had handed her earlier were human, not canine, and had challenged John to find the skull, which, she'd added, probably belonged to a human child most likely male.

Her drugged mind had spouted the information as she took all the clues from the sight before her, and from her memory of Mycroft's tale, to make accurate guesses as to whom the skeleton in the well belonged to. Never had John wished Marie was wrong as much as he had when she'd explained it all to him in rapid-fire; but it seemed, there was some scientific explanation as to why Sherlock took his seven-percent solution when he was placed in a particularly difficult bind.

Inside the burnt-out house, Sherlock continued to stare unseeingly at the floor as he remembered the boy from his childhood once more-

"Victor." Sherlock whispered, and Eurus said softly as she stared at Sherlock intently: "Now it's coming."

"Victor Trevor." Sherlock whispered, his voice shaking uncontrollably.

His face contorted with pain with each passing moment as the full weight of his restored memories sank in, and he whispered brokenly: "We played pirates… I was Yellowbeard and he was..."

Sherlock trailed off, before slowly lifting tear-filled eyes to meet Eurus's gaze as she stared at him intently on the screen, her mouth parted slightly.

"He was Redbeard." Sherlock whispered, his voice breaking as sobs threatened to tear out of his throat.

"You were inseparable." Eurus murmured sadly, before she raised her gaze once more and looked right at Sherlock with those piercing blue eyes. "But I wanted to play too."

Sherlock looked away as he realized what had started his sister's behaviour, what had been the cause and the root of all this calamity.

"Oh." Sherlock breathed as he lowered his head, closing his eyes against the tears that threatened to spill. "Oh God."

It wasn't enough, and a tear spilt out and down his cheek as Sherlock cried softly, before asking between quiet sobs: "What…"

He paused to take a few deep breaths, needing them to control his sorrow enough so that he could continue: "What did you do?"

"I that am lost," Eurus replied in song, "oh, who will find me? Deep down below, the old beech tree."

Sherlock stared down at the ground in grief, knowing now for certain what she had done; realizing the meaning in John's words, and understanding the truth in Marie's deductions.

"Victor." Sherlock whispered, and Eurus murmured softly: "Deep waters, Sherlock, all your life."

Sherlock could only stare numbly at nothing, seeing dark blue ripples like those from the pool where he had first faced off against Moriarty, in the worn ground, while Eurus continued: "In all your dreams."

Sherlock recalled the waterfall from his drug-induced hallucination of the Reichenback Falls, again facing off Moriarty.

"Deep waters." Eurus whispered, and Sherlock remembered the aquarium where Mary had died, while the light from the aquarium fish tanks threw strange blue hues on those present.

"Deep waters." Eurus murmured.

"You killed him." Sherlock whispered, slowly lifting his tear-streaked face to stare at Eurus blankly. "You killed my best friend, as a child."

"I," Eurus answered quietly but with a hint of a dark anger and deep pain in her voice, "never had a best friend. I had no-one."

Sherlock lifted his head to look up in despair at the ceiling, while in the well John struggled to keep his head afloat as the water slowly rose up passed his chest. His one hand clutched the rocky wall of the well, while his other grabbed Marie and hauled her up with him.

She was too weak to hinder or help him – the numb phase of the drugs had worn off, leaving her cold, drained and without any energy as she shivered and her teeth rattled from having been inside the freezing water for over five hours.

"Hang on, Marie." John encouraged, though he was starting to lose hope that they would be saved. They'd always managed to figure something out together, before; but… His heart constricted as he remembered Mary, and little Rosie waiting for him at home.

Marie was deathly pale as she shivered, and she whispered: "Sherlock…"

Sherlock stood unmoving before the screen inside the room in Musgrave Hall, still emotionally reeling from this latest revelation.

"No-one." Eurus repeated bitingly as she stared at Sherlock bitterly.