The mutated zombie sniffs the air as you wander by, weapon in hand, nerves shaking. An attack, of course, is imminent, but the rumbling growl of what used to be a brother in arms sends shivers down your spine. As you press the "W" button and move your onscreen persona down the hallway, you realize something. Fear really is seeping into the atmosphere - and it's coming from you.

Welcome to Doom III. Get ready to scream.

Fusing the cinematic qualities of a "Toy Story" film with the suspenseful elements of System Shock II and Clive Barker's Undying, id Software has put together one hell of a promising first person shooter.

The details, shared at an 11-minute demonstration at the just-completed Electronic Entertainment Expo and a follow-up conversation with id's Todd Hollenshead and Robert Duffy, are still being kept intentionally vague. But what id was talking about was enough to perk a lot of ears.

Doom III's not just about running and gunning. There's a story, written by 7th Guest and 11th Hour author Matthew Costello. The demo shown at the show hints at the plot: A betrayal aboard the Union Aerospace Corporation installation on Mars unlocks the gates of hell, allowing demons and worse to escape. Employees are quickly possessed, their faces reflecting shock, agony, then - finally - malice and hatred as the spirits consume them and take over their bodies. You, somehow, escape the carnage - and it's up to you to find a way to plug the hole and return the world to its rightful state.

There will be NPCs you'll interact with along the way - but you won't necessarily want to trust them all.

As stories go, it sounds pretty standard for a shooter. id, however, insists the plot of Doom III will not be just a loose collection of cut scenes filling space between the devastation.

"The game's story is quite involving" says Hollenshead. "As standard bearers for the industry, we can help from not only the technological standpoint, but from the story standpoint."

(Despite the game's single-player focus, there will be a multiplayer element with a "simple, fun implementation - deathmatch style" says Hollenshead.)

It's the technological side that's drawing the most attention right now - and rightfully so. Doom III's graphics are as spectacular as the screenshots infer. Never in the history of PC gaming have we seen a game this cinematic in real-time. The graphics are so impressive, in fact, that id's having a hard time convincing people that they're real.

Dynamic lighting is probably the biggest of the "wow" factors. Shadows reflect appropriately - on your body, on the walls, everywhere. Those shadows, in fact, are a key element to the game, giving you warning that something big, ugly and hungry is creeping (or dashing) up behind you. Computer monitors glow on character faces - and the glow changes as the data on the onscreen computer does. Heck, mirror reflections change appropriately - and smoothly - as events change during gameplay.

The developer is moving deeper into the sound arena as well, supporting Dolby Digital 5.1 and making it work. Groans of zombies creeping up behind you add tremendously to the fear factor. And the crunch you hear when a zombie bites into a victim will make you shudder.

Weapons on display were pretty typical - a pistol, which slows zombies down, but takes quite a while to stop them; a shotgun, which effectively stops enemies, but has a smaller chamber of ammunition; and a machine gun. The enemies are familiar, but are more terrifying than you might remember. Zombies come in two forms, skinny and fat. Size doesn't appear to make much of a difference in their toughness, though. Imps move in erratic jumping moves, spitting what appear to be flameballs in your direction. They're hard to pin down and harder to kill. The Hellnine beast, rushing at you on four legs - two organic and two mechanical - is a truly terrifying creature that takes a lot of time - and ammo - to kill. (The Hellnine is the creature you see to the right, feasting on a zombie.)

Six or seven creatures were demonstrated at E3. More have already been designed, but were kept out - and id's planning to add a few more before things are done.

While the game is astonishingly impressive, it's also astonishingly violent. id has always been a target for parents groups and other organizations concerned about the level of realistic violence in gaming - and Doom III is going to rally a lot of people to their cause. The 11-minute demo was a bloody gorefest, with realistic splatters and blood streaks. The Hellnine's feast on a zombie in a blood-soaked bathroom was particularly graphic: After dragging the apparently dead zombie in, leaving a bloody streak on the floor, the Hellnine rips into his stomach, ripping out the zombie's (realistic looking) liver and chomping it down, as intestines ooze from the bite wound.

The title, obviously, is for mature gamers, but once parents groups get a good look at what's available, you can bet there will be an enormous outcry. id does not seem worried about this. It will not, however, bait its critics with a long, drawn-out preview/publicity campaign. Now that E3 is over, the company goes back into quiet mode. Hollenshead says not to expect many new screen shots for a long while - and there are no plans to release the 11-minute E3 demonstration as a downloadable movie.

So when do we see Doom III? Right now, id's not getting any more specific than 2003, but given the work that remains to be done, that's understandable. Music and atmosphere, which will be crucial to creating the game's suspenseful element, are far from complete. Nine Inch Nails front man Trent Reznor did the sound work for the E3 demo, but has not signed a deal for the complete game (though negotiations are ongoing). And Hollenshead's note that there are still monsters to be created demonstrates the company is not nearing a finishing point anytime soon.

Trust us, though. If the demonstration at this year's E3 is any indication, it will be entirely worth the wait.