Who are all these people, and why should we care?

At first glance, you'd think that the only thing CBS's "Harper's Island" and NBC's "Southland" have in common would be their Thursday-night time slot.

After all, "Harper's Island" (9:01 p.m., Ch. 2) is a cross between an Agatha Christie novel and a slasher movie. A whole lot of people are on an island off the coast of Washington, and somebody is killing them off at a fairly rapid pace.

(Two episodes, five fatalities.)

And "Southland (9 p.m., Ch. 5) is a gritty police drama about a whole bunch of cops handling tough crimes in the worst parts of Los Angeles.

And yet, after two episodes of each show, they share exactly the same flaw. There are so many characters that it's impossible to keep them straight. Or to care a whole lot about them.

It's a problem that's particularly pronounced in "Harper's Island." The writers/producers have done a nice job with the murders so far — tied up under boat, ground up by propeller; stabbed/cut in two; beheaded; hanged; burned alive.

There's a visceral reaction, but not an emotional one, because we barely knew who these people were. We never met Victim No. 1, as a matter of fact, and had just been introduced to Victim No. 3.

This is very much in the vein of theatrical slasher films, but those are generally two hours or less in length. "Harper's Island" is 13 hour-long episodes spread over three months.

As for "Southland," maybe we'll find out who these people are if it lasts a few years. We're getting information in dribs and drabs, but at least there's progress.

And we're promised that in tonight's episode, "when Officer Ben Sherman (Ben McKenzie) reveals details of his past to the department therapist and his training officer, John Cooper (Michael Cudlitz), the motivation behind his decision to be a cop becomes clear." After two episodes of vague hints.

Actually, that's one similarity "Southland" has with "ER." Fifteen years ago, it took awhile for us to discover all the doctors' and nurses' back stories, although things moved at a faster pace than this.

I still have high hopes for "Southland." On the other hand, I'm getting rather discouraged about "Harper's Island."

IT COULD BE WORSE. Take, for example, the show that ABC airs opposite "Harper's Island" and "Southland" — "Private Practice."

I know who all the characters are on that one. And, yet, I still don't care.

Hey, wouldn't it be cool if they combined "Private Practice" and "Harper's Island"? ("Private Island" sounds better than "Harper's Practice.")

Anyway, if somebody ran around murdering characters on "Private Practice" every week — and they all deserve the death penalty for being so darn annoying — then I'd watch. I'd make a point to watch, actually.

That would be entertaining.

E-mail: pierce@desnews.com