And after the first five episodes of the season, Lupo's rather interesting back story gets even more interesting.

Of course, plot is still primary to "Law & Order." And Sisto said that he's become a big fan of the show's style.

"It is just a different format of focusing on these particular cases," he said. "And so there was that — trying to understand that whole kind of genre of television — and I've become obsessed with it. That's all I watch now. My TiVo is filled with 'Law & Orders' and everything. You know, I really do love the format."

That format doesn't change this season. The characters have been shuffled a bit — in addition to the addition of Detective Lupo, Jack McCoy (Sam Waterston) has been appointed the new district attorney, and there's a new lead prosecutor, Michael Cutter (Linus Roache).

"I think that the show is going through one of its major renovations of the past 10 years," Wolf said. "The show has a very different look than it had two years ago."

He pointed out that two years ago, Waterston (now 67) was the lead prosecutor, and Dennis Farina (63) was the lead detective; now Roache (43) is the lead prosecutor, and Sisto (33) is the new detective.

"That is a very, very large shift and also a very deliberate shift to hopefully reignite or further penetrate a younger demo," Wolf said. "The show has been skewing older, and we would love it to skew a little bit younger."

Not that that should drive away any of the show's older fans. "Law & Order" is still a show that, once you sit down and start watching, it's hard to turn away.

(Heck, I can tell you from recent personal experience that once you sit down with five episodes it's hard to turn away. I can't give a show higher praise than that.)

And, by the way, through the first five episodes of the 18th season, we learn almost nothing about assistant District Attorney Michael Cutter's back story ...

• When "Law & Order" opens its 18th season tonight at 8 on NBC/Ch. 5, a couple things will have changed. Which, of course, means nothing at all has changed.

The show, which has gone through myriad cast changes over the years, goes through a couple more tonight. On the "Law" side of the equation, Jeremy Sisto stars as the new police detective, Cyrus Lupo. Sisto is replacing Milena Govich, who played Detective Nina Cassady.

And over on the "Order" side, Linus Roache comes aboard as new assistant District Attorney Michael Cutter, replacing Jack McCoy (Sam Waterston).

Waterston, however, hasn't left the series he joined in 1994. His character is the newly appointed district attorney, replacing Arthur Branch (Fred Dalton Thompson). Thompson, of course, did leave the show — to run for president of the United States.

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E-mail: pierce@desnews.com