Amariah fetches down their alethiometers.
"It's about time I took care of Alethia's afterlife, whatever it may be," she says quietly. "What can the alethiometer tell you about what I'll find?"
Cam tries assorted phrasings to get answers out of the alethiometer that might help find her.
Kas tries, too, and he just pushes the meanings directly to Sherlock through the link.
There.
That is Shell Bell, and that is a harpy. She gives the harpy a telekinetic shove as she comes to a stop just beside Shell Bell.
Shell Bell looks up just long enough to identify Sherlock's face and then she flinches away.
The smew has quieted, but he's still shivering.
"Put her down, let us go," says the smew, "forget about us."
"Absolutely not. It is obvious that you intend this abandonment to benefit me. It will not. I refuse to allow you to make that choice on my behalf. Tell me what happened."
"She screamed," Shell Bell whispers, "and I remembered, everything bad I ever did, ever thought, and I felt it, and I still do, and it's terrible, and I'm - so - selfish I still don't know what to do -"
"If she made you think that leaving me was some kind of moral duty, then she told one of the worst lies I can imagine, whether or not she did it using the selective application of individual truths."
"I wished you dead, I did, I wished you dead - and hurt and away from Tony - just because I wanted you where I was," sobs Shell Bell. "And when I told you before all I said was please still love me like that made any sense -"