Another episode with sinister overtones from series creator Joss Whedon, who seems incapable of writing a bad story.
This episode demonstrates two of his greatest strengths as a writer: the ability to create interesting and memorable characters very economically (here, for example, there's the foppish Diego - formerly Marvin - and the fawning Chantarelle, whose wish to join "the lonely ones" is totally believable); and his seemingly effortless skill at creating snappy dialogue.
There are countless examples of this throughout the episode, and barely a line is wasted. Whedon makes it seem like other writers finish their scripts before adding in the wisecracks and teen-talk. His dialogue rarely seems contrived or out of place, and brings real personality to his characters.
There's a terrific piece of dialogue at the end of the episode which smartly captures the tone of this episode.
Giles is consoling Buffy after she was forced to stake Billy: "It's terribly simple. The good guys are always stalwart and true. The bad guys are easily distinguished by their pointy horns or black hats. We always defeat them and save the day. No-one ever dies, and everybody lives happily ever after…" Buffy's response is swift and tinged with bitterness: "Liar!"