I have taken to watching most of my television via iTunes. I caught Mad Men that way, at least for the first bunch of episodes, and one episode entitled “New Amsterdam” spurred me (almost by accident) to order the pilot of the Fox show New Amsterdam.

This show about an “immortal” cop lacks something. Of the shows I have purchased, it is one that I will be unlikely to follow-up on. Of the recent fantasy-gimmick shows, it strikes me as “not quite working,” while the more pedestrian and Quantum Leap-like Journeyman strikes me as far more watchable. (Is that why it has been cancelled?)

Showtime’s Dexter, on the other hand, is almost flawless television drama. Here we have a clever high concept expertly fleshed out: a serial killer who lives by a code, killing only killers who have escaped justice. Our “hero” works as a blood splatter analyst for the Miami Police Department, and must juggle his hobby and job and . . . stay alive.

The American obsession with fictional serial killers is itself fascinating. The idea of deviltry is there; our view of them is as almost uncatchable beings — seemingly omnipotent — whom we love to hate and hate to love. The character of Dexter is especially well done, since he also plays the technical role of angel, avenging the innocent by killing the guilty. It is easy to dismiss such a high concept as going against the grain of the civilized need to quell vigilantism, etc., but in fiction one contemplates not reality but selected slices of it, distorted by the lens of art. For a purpose. We are indeed brought back to the time when people believed in literal angels and devils. The serial killer obsession — especially in its idealized horror form, in fiction — is as easy to explain as are past obsessions with angels and devils.

We want to contemplate Power. And we want to see stories influenced directly by the play of the extremely powerful. Principalities and powers, folks.

Perhaps this same lust helps explain why so many people can tolerate for such long times the gruesome personages of high-end politics: kings, generals, presidents, et al. The drama of power fascinates, as does picking at a scab.

And of such obsessions, art may flow. Like blood.