Select episodes from first season available online at (and soon, I hope, on Hulu). Season two debuts Monday, September 21, on ABC.

I recently read an interview with a short story author who said she enjoys writing short works because she feels more freedom there to explore extremely dark, bleak places—places she would be reluctant to visit, as either a writer or a reader, for the length of a novel. The idea rang true to me (partly because I’m presently in the midst of a provocative but depressing, emotionally draining novel that I wish were a bit shorter), and although I think the notion could easily be taken too far (perhaps it would be better to say that that overwhelmingly dark subject matter is more challenging in a novel than in a story), I find it fun to extrapolate from that notion to other media.

For example, musical devices that might be tiresome in a longer work—gimmicky orchestration; the incessant drill of a single rhythmic pattern; light accompaniment of a guileless melody—can be charming in a short piece (see: Sabre Dance). A movie can use simple, archetypal characters that would become flat and tiresome in an ongoing work like a TV show (see: Pan’s Labyrinth). And a TV show with a charismatic lead character often can get away lackluster storytelling because spending time with the character is the whole point of watching the show.

Such an encapsulation would be a little harsh for Castle, ABC’s one-year-old mystery drama, but not by much. The premise is gimmicky, the policework is standard, and the mysteries vary in quality (to be fair, that’s typical of crime shows), but none of that really matters because Nathan Fillion is the star: Castle is fun and compelling to the extent to that Fillion is fun and compelling, which makes it quite fun and compelling indeed.