TV writer & blogger Will Dixon has taken some points I raised on how mysteries are constructedand expanded on them as they apply to sf, horror and fantasy shows . He wrote, in part:
when it comes to constructing the plot for good genre mysteries (like X Files; Buffy; Angel; Firefly…and today you've got Supernatural; Smallville; Warehouse 13; Sanctuary; even Chuck, etc.), there is one question always be asked:
What is it…what is it really.
(In the case of procedurals and investigative mystery programs like 'Veronica Mars' or 'Castle' or 'Bones', the mantra becomes: Who is it...who is it really.)
[…]Of course, this is just one aspect to telling a good mystery story. To take it to the next level, you also need to pick an overall theme to flesh out the episode.
Dixon offers some examples from Buffy The Vampire Slayer to back up his points. His observations are well worth reading.