He pulled the trigger and the room erupted in a cacophony of gasps punctuated by two agonized screams.This kind of story has a very narrowed focus: sadism. It is much like pornography in that it only caters to those who like reading about sadistic torture and murder but rehashes it very well. As I am a nightmare fetishist in a very real sense, I suspect my earlier enjoyment of such sadism was of masochistic appreciation, though I am unsure if that was the expected appeal.
"Ooh...such pretty music," Drusilla crooned, twirling about the room and then hovering over her lover's shoulder as he reloaded the bow. "Like angels playing harps with bleeding fingers. Can we make them play some more?"
This kind of horror story for normal people would direct its gruesome imagery toward eliciting negative emotions. I understand most people would find the idea of two sociopathic sadists creating pain and hopelessness to be entirely horrific with no erotic appeal, so this would have only the appeal of horror literature. People sometimes like drowning their brain with negative emotions. It has similarity to masochism but is not of a sexual nature. I find it likewise fascinating.
On the other hand, it could just be sadistic catharsis. We could be expected to identify with the killers and enjoy their mayhem. I recall a When They Cry fanfiction, "Laughing All the Way", based around the author wanting to let out her frustrations through writing sadistic mutilation. "And Then There Were Three" could be based around a similar concept.
Regardless of it being simply an exercise in sadism, the characterization is great. Everyone seems to have their voices intact. I love Giles dryly interrupting Spike's evil commentary. I can just hear him doing that! I also like how the Spike/Buffy attraction is handled without getting rid of it completely to assert the Spike/Drusilla relationship, but instead keeping it around in some form without being in focus. It seems like a believable evolution of the Spike character after "Crush".
The biggest problem is the spelling not always being great. There are a few typos that change words into other words, like "steel" being written as "steal", which a spell-checker wouldn't catch. It's pretty jarring to see Angel being referred to as "Angle". This is why betas are sometimes important. Again, glass houses.
The ending is a bit of controversy for me. On the one hand, it's a cool creepy vampire ending with Buffy being killed by the evil undead... On the other hand, they really could keep her around to have fun with longer. In any case, it's a cool horror story with a simple purpose that's done well.