"Could be. I don't have a lot of practice with the vampire senses, so it's hard for me to estimate how strongly the smell of Giles is going to pervade a hall he was briefly dragged along."
"Fair enough. I'd recognize Giles's voice, if he happened to be talking... loud enough to hear through a door, my senses boosts are pretty trivial except in terms of what happened to my reaction time."
"If either of them happened to be talking I could place their accents, which would be a big hint."
"Yeah, especially since the lady didn't need to ask clarifying questions." Stroll stroll down the oddly carpeted hall.
Pause.
Closer inspection of the door that smells ever so faintly of Giles.
Sherlock listens to this exchange, glances at Bella, and raises his eyebrows. What excellent timing they seem to have.
When the door opens, the person opening it is Very Startled And Confused!
"I - this is not what you were supposed to -"
"No, I was supposed to kill him, probably, because all the vampires I have already killed are meaningless when you want to know if you can sic me on whoever or whatever suits you like I'm some kind of assassin-cum-slave labor. Well, I failed your test alive. You want to try to fix this imbalance? Giles, it is an enormous relief right now that you are tied to a chair; should I be scared of this creep?"
"Probably not," says Giles. "He has stakes and a gun, but I don't believe it's loaded."
"Now see here, young lady -"
Now the asshole is on his face on the floor with his hands pinned behind his back and a knee in his sciatic nerve. "I have a name. I'm going to assume you know it. Or you could go with a nice, respectful 'Slayer'."
"Slayer," says the asshole against the carpet, "attacking a human being is -"
"- what you did to me this afternoon," says Bella sweetly. "Sherlock, can I get you to untie my Watcher and call my dad, please?"
He unties Bella's Watcher. He calls Bella's dad.
Bella's Watcher eyes the strangely helpful vampire suspiciously, but doesn't try anything.
"We have found the man who kidnapped your daughter," says Sherlock. "She has him under control."
"Thank you, Sherlock. Giles, what is this tweedy creep's name?"