"What do you need him for?"

"Native guide. Is this a social conversation or are we still trying to talk our way out of a fight?"

"I think your vampire is maneuvering for my assistance in retrieving the Gem of Amara. I'm not currently interested in fighting either of you but I'm going to be a harder sell on finding the Gem and not immediately destroying it."

"Because, what, you value the option of being able to kill him without having to steal from him first?"

"Granting for the moment that he's completely innocuous and it would be very helpful to make him in particular immortal, someone else might steal it from him, and the Gem of Amara is famous for its ability to turn ordinary vampires into huge problems. I don't like huge problems."

Sigh. "Why do you even want her help? How helpful would she be?" Promise asks Tea.

"She's doing late-night research in the library where all of the useful books we've been reading are kept. And she's the Slayer. Slayers come with Watchers, who are members of an organization known for having a lot of useful books, among other less relevant characteristics; it follows that her Watcher is probably the librarian and very familiar with his useful books. If she asks him where to find the Gem of Amara, he'll be able to locate that information in his own library much faster than I can if it is there at all. That also goes for anything else we might like to look up."

"So you want his help, not hers."

"You could put it that way. I also want her open cooperation in the endeavour because it would be inconvenient if she decided to destroy the Gem rather than let me keep it."

"And that seems like something she's likely to be able to do."

"It would be inconvenient if she sought to, regardless of whether or not we could successfully prevent her," he says.

"Fair enough. And it would be awkward to just store you in Fairyland indefinitely since we don't have animals."

"Yes."

"I am open to being convinced that I should let Mr. Holmes have the Gem of Amara," says the Slayer.

"You know better than I do how you're planning to prevent someone from stealing it from you," Promise tells Tea.

"The Gem is only a temporary measure anyway. I don't expect to have much trouble keeping it."

"A temporary measure on the road to...? Well, how about this. I think I can hook you up with a solid ward against sunlight. If I give you that and don't find myself disappointed in your behaviour afterward, I'll consider helping you find the Gem."

"Perfectly reasonable."

Huh.

"I'd also like to know just what happens if you hear my 'real' name, and what a 'real' name is, before I let you get any closer to my Watcher," she adds.

"Your real name is the first name you ever had. If I know it then you can't hurt me and I can give you enforced commands."

"Noted. How widespread is this property? Should I be worried about encountering other fairies who might be less friendly about it?"

"All fairies have this property and most of them are not as nice as me."

"Best guess, Promise is currently the only fairy of the relevant category on Earth," says Sherlock. "It seems unlikely but not impossible that that might change anytime soon."