A/N- This is a series 3 AU. If you want in on the ground floor, After the Fall, on my profile, is the one to start from :)

"Fiss, Daddy! FISS!"

John shifted Charlie's weight on his hip and offered up a smile, somewhat pained. "Yeah," he said. "Lots of fish."

If there was anything that could be said about the local aquarium, it was that it definitely had lots of fish. The perfect place to take Charlie on a rain-soaked Sunday afternoon in late November. Charlie had spent the earlier part of the month sick with tonsillitis, an on-again-off-again misery which had finally resulted in a hospital stay and a tonsilectomy. Since then she'd apparently made a full recovery, but Molly had become obsessed with the idea that their sixteen-month-old daughter was now regressing with her speech. Charlie liked fish. Seeing fish might encourage her to talk more, and even though John was now back at work three days a week, both he and Molly still had weekends free for family outings. This one had so far been a raging success - for Charlie, anyway. She had hoarsely squealed "FISS!" at every fish she'd seen for the past hour and a half.

"Daddy…" She struggled against his grip until she was close enough to the underwater viewing glass to plant both sticky palms on it. "Daddy, look! Fiss!"

John looked over his shoulder at Molly, hanging back holding onto the pram, which was stacked with their bags and coats. "I never want to look at another fish again," he muttered to her.

Molly smiled. "So that's a 'no' on getting her a goldfish?"

"I've already said it's a 'no' on the goldfish, Lolly. We have cats. Anyway, she's too young to look after a fish. It'll die, and then we're going to have to explain to her about Fish Heaven."

Before Molly could reply, a large, balding man in a brown bomber jacket breached the gap between them, then elbowed John aside until his nose was almost on the viewing glass. "Kids!" he roared. "Come and have a look at this!"

Two… four… no, five children. As he stepped aside to let them through, John counted his mercies. Behind them was an exhausted-looking, frail, fortyish woman who held about four coats in her arms and who seemed even less enthusiastic about 'fiss' than John Watson.

The man banged on the glass with both fists. "Why doesn't it do something?" he said. "Christ above, I paid ninety pounds - ninety pounds - to get in here, and that's not including feeding the seven of us, right? If I knew it was going to be this boring, I'd have taken the kids to the zoo instead."

"It's a fish," John said. "And it's, y'know, swimming around in its tank. What else did you expect a fish to do?"

The man gave him a filthy look. "Shows what you know, mate," he said. "It's a shark, not a fish."

"Okay," John said. He rolled his eyes back at Molly, who smothered a giggle.

The main attraction in this tank was, in fact, a huge Mako shark, nearly three metres long, with sides that gave off a metallic gleam and a snout like a rapier blade. A sign, adorned with painted barnacles and sea shells, let the visiting public know that the shark's name was Marvin and that he was a brand-new arrival at the aquarium. While the man in the bomber jacket may have been unfair in his expectation of how entertaining a fish should be, John had also expected a shark to be a little more animated. Besides the odd restless flick of its tail, it seemed to be drifting through the water, rather than swimming. Glassy eyes - but then, sharks always had glassy eyes. As the boisterous, grubby children crowded in for a better look, the man banged on the glass again, completely ignoring another sign nearby: Please don't bang on the glass. It frightens me!

"Looks like we're done looking at the shark," John said to Molly. "And I'm desperate for coffee. Do you think they sell any here that we can afford without taking out a bank loan…?"

Charlie screwed up her nose and demonstrated another word she'd learned during her recent illness. "Daddy," she said quietly. "Fiss sick."

John turned back to the tank just in time to see it. The Mako accordioned itself, as if it were gearing up for a sneeze. Then its head shot forward, three times in quick succession, and a rust-brown cloud erupted from its mouth and billowed into the water around its head. In amongst it, a large, fleshy lump drifted toward the viewing glass. John caught a glimpse of an emblem on it - two boxers in fighting stance. A tattoo.

"Oh, God," he said.

And that was when the screaming started.

There must have been police in the area already, because a pair of uniformed officers arrived within ten minutes - an impressive response time, even if they'd had the actual victim on-hand bleeding out. Detective Inspector Greg Lestrade and Detective Sergeant Sally Donovan were only a few minutes later. By the time they arrived and made their way to the area the responding officers had taped off, it was to find Molly on her hands and knees on a tarpaulin, examining the lump of flesh - obviously a human arm - and occasionally poking it gingerly with a ballpoint pen. There was a blank notebook open beside the arm, and she was, oddly enough, wearing latex gloves. John, who still had Charlie in his arms, was having an animated conversation with a balding, tanned man in his late fifties, who was so short he barely came up to John's shoulder.

"Family affair this time?" Lestrade said. "How'd you get here before I did?"

"We were already here," John said. "You know it's a good day out with your toddler when she gets to watch a shark vomit a human arm."

"Fiss," Charlie explained.

"Bet you've never seen a fish do that before, Charlie." Lestrade reached over to tweak her chin playfully. She hid her face in John's shoulder for a second, then looked back up at him with mischief in her brown eyes.

"Yeah, she's definitely her mother's daughter," John said proudly. "Wasn't the least bit fazed. Might have a future doctor on our hands."

Molly glanced up at her husband and smiled.

"Oh. This is Brian Crouch," John said, taking a step back to let the older man come through. "Directing Manager of the aquarium."

Lestrade introduced himself to Crouch and shook his hand, firmly but politely. Then he introduced Donovan, who immediately asked, "So where's the shark?"

They looked over at the viewing tank. It appeared to be empty, except for a few guppies and a couple of starfish.

"In our hospital tank," Crouch explained. "We needed to isolate it from the other animals straight away."

"So you removed it from a crime scene," Donovan said. "Well done."

Crouch raised one eyebrow. His eyes were a curiously clear, hypernatural grey, as if he were wearing contact lenses. "This isn't a crime scene," he said. "No crime was committed in this aquarium, Detective, I can assure you."

"Well, that's what we're here to find out," Lestrade said. "The shark swallowed the arm somewhere. Donovan, do you want to go with Mr. Crouch to the hospital tank? I'll be right there with you, once Forensics show up and take over."

"Sure," she said. "Let's go look at this shark, shall we…?"

John knew this for the cue it was, and said nothing until both Donovan and Crouch were out of sight and Lestrade had sent the responding officers to find Centre Management and advise that the Aquarium be closed until further notice. Once they were alone, he said, "I called Sherlock, but it went to voicemail."

"Yeah, I just left him, actually," Lestrade said. "Down at the docks, poking around a yacht."

John frowned. "He didn't tell me he had a case."

"Well, maybe he thought you might appreciate a day off," Lestrade said, genuinely trying to be comforting. "He didn't think it was anything thrilling, anyway, until this happened."

"This? The arm?"

Lestrade nodded. "Three missing people - a family by the name of Holland. Brett, his wife Sadie and their two-year-old daughter, Maisie. A friend of Brett Holland, Derrick Rice, found the yacht abandoned off the coast of a village called Mousehole, in Cornwall."

"You're thinking they were murdered?"

"We don't know yet, but it's looking likely. Going missing isn't a crime, but a whole family, including a toddler?" He shook his head. "There's no other reason for them to completely disappear, anyway. According to Rice and the Cornwall Area Command, it's like this family was just beamed up into the sky. When there was no radio response Rice found the yacht, couldn't get a visual, and boarded. All the Holland's stuff was still there, including their clothes, Sadie Holland's epilepsy medication, and all the navigational equipment. There was a live canary in a cage in the cabin. And get this: there was food laid out on plates in the galley. And when the first responders got there, it was still lukewarm."

John thought about this. "Abandoned the yacht in a hurry," he mused. "They must have thought it was going to sink..."

"Which is where Sherlock comes in. The Cornwall force said the yacht - the Marie Celeste - is perfectly seaworthy, not a thing wrong with it, with full radio access. It was barely a mile off-shore, and the inflatable liferaft hadn't been touched - if they abandoned ship, why didn't they take the raft?"

"... Pirates?"

"No blood, no signs of a struggle."

"So they just sort of… disappeared?" John looked down at the lump of flesh, with the two boxers still facing off on it. "I think I'm getting this," he said.

"Yep." Greg gestured to it with one finger. "That tattoo. Apparently, Brett Holland had a tattoo of two boxers fighting on his right bicep. We'll need to run a DNA check, and fingerprints, if they can be lifted, but I'd say that's him. Or at least, part of him. Eaten by a shark."

"In Cornwall? In November?"

He shrugged. "I'm told it's not impossible. Climate change and all that."

"Well, I'm not an expert either," John said. "But it seems a bit… weird."

"Either that, or someone broke into a secure aquarium to feed the shark, when they could've just tied a brick to the body and dumped it in the river."

"Or buried it somewhere." John glanced over at Molly again and saw that she was still diligently writing notes.

"Exactly. The Cornwall Area Command weren't getting anywhere with it and referred it to the Met. We got an order from on high to tow it up here to the maritime headquarters for further inspection. Sherlock's having a look around now."

"What's he think?"

"What does he ever think?" Lestrade said. "I did hear him muttering something about the canary, but if I understood what he was talking about, I wouldn't need him, would I?"

John pulled out his phone and poked at the display screen with his thumb. "Three texts," he said. "Two missed calls. I'd better call him back, Greg, let him know what's happened. See if he wants us to text him photos of the arm, or whatever."

Taking Charlie with him, he wandered a few metres away to the perameter of the police tape and put the phone to his ear. As Lestrade turned back to Molly, crouched awkwardly on the tarpaulin, he heard John open the conversation with, "Well, it finally happened, Sherlock. Two tens going on in two different locations…"

Lestrade got down on one knee beside Molly. "How'd you convince Crouch to let you have a poke around like this?" he asked her.

She smiled, picking up the notebook and resting it against her knee while she drew a rough sketch in it. "My hospital ID," she said. "It was in my handbag. Um… I don't mean to be difficult, but I don't think the victim was eaten by a shark, Greg."

"John said you saw the shark puke that up. How could he not have been?"

"Oh, I meant, I don't think that's what killed him." With her pen, she pointed to the severed end of the arm. The macabre bundle gave off a strong smell of brine and two-day decay, and something revoltingly fishy besides, but Molly appeared not to notice it. "The shark looked far too small to have swallowed a whole person, which gave me an idea," she was saying. "I'd need to see the flesh under microscope to be able to say for sure, but this wound isn't consistent with a bite. Teeth make a ragged mark on the flesh. This is far too neat for that. And teeth splinter bone, but that one's cut cleanly through. And look at this, here…" She pointed to a spot on the purple, rubbery flesh.

"That's… oh, bugger. That's rope burn, isn't it?"

Molly nodded.

Lestrade leaned back on his heels, thinking. "So he was tied up and his arm cut off," he said. "Don't tell me he was alive when they did it."

"I can't tell just by looking at it here," Molly said. "But maybe. Corpses don't get rope burn like that. Greg… if Brett Holland is dead, what happened to his wife and daughter?"