By Mike Flaherty
Updated March 30, 2001 at 05:00 AM EST

It’s a brisk late-winter afternoon on the suburban L.A. side street that’s serving as the set for CSI: Crime Scene Investigation — CBS’ little forensics drama that could — and for once it’s not just the silver-slabbed corpses that are dead on their feet. ”We’re tired,” says William Petersen, who not only plays hyper, eccentric crime-scene investigator Gil Grissom but also produces the series. Cause of exhaustion: After getting a delayed go-ahead during pilot-pickup time, the show has been playing catch-up ever since and is currently racing to crank out the season’s last few episodes. ”The crew is killed,” says Petersen, 48. ”All we do is go to work and try to [tape] these stories as fast as we can. That’s the pressure of it once you become something.”

For costar George Eads, 34, who plays Texas-bred clue sniffer Nick Stokes, ”it’s like the Tour de France where you just kind of keep your head down and keep pedaling. Every now and then you dart out of the place you’re in, but you don’t look up.”

Meanwhile, deep inside a windowless room at the show’s Santa Clarita, Calif., headquarters is where you’ll find the creepy epicenter of the show’s dark brilliance: A group of seven writer-producers hunker down around a fluorescent-lit conference table determined to ”break” (i.e., flesh out) the season’s remaining story lines. There’s talk of a fast-food massacre reminiscent of a 2000 New York City bloodletting, and a new truth-telling technology called brain fingerprinting that could come in handy as a narrative launchpad. But the most twisted plot proposal of the day involves feral hounds, a devious fitness expert, and a particularly grisly protein drink (hint: The Donner Party would be whipping out their straws).

The crew goes on to discuss another scenario in which Marg Helgenberger’s character, Catherine Willows, will be assigned to determine the cause of a building collapse. Turns out she’ll be placing a chunk of the structure inside a tank filled with rubber Superballs and then bombarding it with Beethoven’s Fifth Symphony (and you thought all that myocardial mumbo jumbo on ER was confusing), only to discover that — thanks to an array of physical principles way too complicated to get into here — 50 years’ worth of high-decibel sound from a nearby airport was one of the culprits. Geeky and arcane? You bet, but that’s just the kind of minutiae CSI — and its fans — revels in. Says Helgenberger, 42: ”I think the fact that the science became much more the star of the show than anyone anticipated was a big surprise.”

Not to CSI creator (and amateur science buff) Anthony E. Zuiker, who’s currently sitting at the far end of the writers’ room, flanked by an edition of Primate Anatomy (for an upcoming gorilla assault episode, don’t you know), while a staffer across the table holds a well-worn copy of Practical Homicide Investigation, a seminal forensic-science text. ”What makes me so proud is that these are the kind of books you need on your table in the third year, not on episode 18,” says Zuiker. ”We’ve really come a long way in terms of our twistedness and our coolness.”