Hilarie Burton and Chad Michael Murray, <EM>One Tree Hill</EM> Hilarie Burton and Chad Michael Murray, One Tree Hill

For three seasons, One Tree Hill has been a quiet WB gem among the likes of the quippy Gilmore Girls and the big fun of Smallville. Equal parts addictive teen soap and absorbing family drama, the series is set to gain some well-deserved attention with a school-shooting episode, airing tonight at 8 pm/ET, that could be written off as one of those "very special" clichés if it weren't so... very special.

"It's big on a number of fronts," says executive producer Mark Schwahn. "I felt a sense of responsibility [in telling this story] that I don't know if I've ever felt before. This episode deals with something that is happening in the real world the rise of violence in our schools. And to have the opportunity to address something that's happening now, almost weekly... it's actually heartbreaking."

As is the episode. Two and a half minutes into the hour  which for the most part is eerily devoid of the show's signature emo soundtrack Tree Hill High outcast Jimmy Edwards (Colin Fickes) opens fire in a crowded hallway, triggering not just panic among his classmates but also an examination of the bullying that drives teens to isolation, self-abuse and, in this case, a level of violence that claims two lives.

Immediately following the shooting, the school is plunged into lockdown mode, leaving Lucas to tend to a critically injured Peyton, while Nathan, Haley, Skills and several other students find themselves trapped in a classroom with the increasingly unstable Edwards. But unlike, say, the never-again-mentioned death of Beverly Hills 90210's gun-crazy Scott Scanlon, Schwahn hints that survivors and viewers alike will not be able to forget the crisis or the shattering final 10 minutes of the episode very soon.

"The way one of [the deaths] goes will be unexpected. It's harrowing," reveals Schwahn, who expects to face fans' wrath for killing off a major and beloved character in such a brutal, coldhearted manner. "I do feel like there will be a part of the audience that may feel betrayed a little bit. They show up each week to spend an hour in this safe world, and now it's not safe."

What is safe is to say that nothing will be the same for any of the key players after this week.

"Everyone involved in this episode understands this moment as a tragedy," Schwahn says. "How they respond to it is storytelling gold. Some of them will go really dark. Some of them will be unable to recover emotionally. Some of them will understand that life is very short and precious and that they need to stop being afraid of the things or people that they want in their lives."

Which means that there could be fallout for months to come. In fact, Schwahn guarantees it. "Most shows would have saved this for their season finale. I designed this [as a way] to propel us toward our end-of-season cliff-hanger."

A cliff-hanger, mind you, that promises to be as suspenseful as the one going on behind the scenes. As UPN and WB prepare to merge into the new CW network, there is still no definite word on OTH's fate. "I don't think we'll get word until right before the [May] upfronts. I think we're certainly on the bubble.... We'd like to be included."

Schwahn does reveal, however, that if the show returns in the fall, the new season would cover the second half of the gang's senior year. But with that determination of its fate still months away (and fans rallying to spare the underrated drama at www.PetitionOnline.com/saveoth), he admits that tonight's stellar episode is also his riskiest.

"The network and the studio were very afraid of the episode because of the content. Mostly about Jimmy Edwards," he says. "The episode is about this kid.... And then there's this big soapy moment at the end that's not about him. And that's dangerous. Because if you take off the end's [twist], you have this huge, pro-social story that you could have a town meeting about. I think you still could. There's just the extra little piece that is so shocking... but it still fits. It absolutely fits."