Shell doesn't know how long it's been. She doesn't know where she is. She doesn't know how to get home, or if she has one.
She stands on Voice's doorstep. She blinks slowly at the brightness.
She walks in a random direction.
Downsiders aren't big on charity. It's not like it's going to kill her if she doesn't get help. It's not like she's unfamiliar with the effects of dehydration and hunger; Voice didn't always remember to take good care of the pet in the basement. Shell walks, and when she's tired she lies down on the ground and sleeps, and when she wakes up she walks, and every few days she curls up on the ground, waits to torch from thirst, and then gets up and goes on.
She doesn't count the number of times this happens. It doesn't matter.
She walks. She has nightmares. She walks.
On an unremarkable day on an unremarkable street after unremarkable stretches of years, she feels herself cross a telltale threshold of dizziness and headache: she cannot make significant forward progress towards Not Where She Is Currently Located until she torches or (less likely) someone gives her a lot of water. It's possible she'll be able to sleep through this torch. She sits. She leans on a wall. She should probably pick up the next sharp object she finds. Maybe a piece of broken glass will present itself. Then she can skip these parts.
She sits, and she closes her eyes, and she waits. If the buildings around her would ever have seemed familiar, they don't now.
"...Why not? I'm fine. And now we know. And if I hadn't been fine, you and Sherlock and Tony would still be fine, and I'd either stop existing or go back to Downside but you'd know to look for me if you wanted me back again, everything would be fine."
"You are slightly more redundant than the average Bell, that doesn't mean you should torch yourself without knowing for sure whether it works while Sherlock is holding you," says Bell.
"...Oh. Oh, Sherlock, I'm so sorry, did I scare you - I thought it would be okay, you have another one, you have the right one right there -" Shell turns her face into Sherlock's shoulder and scrunches towards herself apologetically.
"I love you too, but I shouldn't've started existing so I didn't think it'd bother anyone if I took a chance of stopping when the one who should exist is there, I didn't think, I'm so sorry."
"Hey," Tony says gently, hugging her again. "If anybody knows what it's like to feel like that, it's Sherry. It's okay. We love you."
"No no no you have to exist," says Shell to Sherlock, alarmed. "You are very important, and there isn't an extra one of you, either."
"Good. You need to understand that. You never did. I wouldn't even be half sane if it wasn't for you, if I hadn't had - the fact that you existed to hold onto." Shell switches to addressing Bell. "You're thinking the sanity cut was only because it was a long time, and you're right that it didn't help, but I didn't even hold up very well through the very first time, you're thinking Golden hurt worse when she turned and Amariah more invasively when Path was kidnapped and that's true but they both had people who loved them, there, holding them the entire time. We need that. We need to tell all of them that they need that, I don't think anybody but Golden understands and she thinks it's only because of the mate bond."
"You're right. I was thinking that," murmurs Bell. "...It's good that you at least notice you're not all that sane."
"It's obvious," says Shell. "Obvious. We should be mostly you. I can just tuck away in a corner of you to do torching and memories of Downside." She pauses. "Oh, we're probably going to fuck that place up, aren't we. I was thinking of doing that before Voice got me."
"That place," agrees Bell gravely, "is very much going to get fucked up. ...Sherlock. Sherlock, I can see you thinking that. Do you need Shell to cry on you some more? Would that even help?"
"What?" asks Shell. "...Would it help something if I did? I can. It wouldn't be hard. I can't read what you're thinking anymore, Sherlock, what's she seeing...?"
"Is it the kind of moment where you don't believe me that you're very important, even though it is literally the only thing that is so true that I could still remember it after Voice when I thought I'd invented all our alts and that there was ever such a thing as magic and my own name? That kind of moment? Will it go away if I cry on you again?"
"I believe you that I am very important to you," she says. "It is extremely obvious that I am very important to you. It is very important to me that I am very important to you."
"But - but - no, you've just been putting up with it, that she thinks like that, but it's going to drive me just nuts!" Pause. "...A tiny, tiny bit more nuts?"
"I'll let you monopolize her in the couple days we spend double-checking merger parameters, see what you can do - if you can't get any farther than that, we're keeping my attitude towards the issue," sighs Bell.