Towards the end of last month, someone leaked eight minutes of Modern Warfare 2 campaign footage onto YouTube. As I'm sure was the case with many of you, I was immediately torn between the desire to satisfy my curiosity, and the knowledge that what I'd be watching would be both low in quality and packed full of spoilers. In the end I mustered enough willpower to steer clear of the video, and I'm now glad that I did: last week Activision and Infinity Ward allowed me to see the same level, "Takedown", demoed live in HD, and it was certainly worth the wait.

This episode takes place in Rio de Janeiro, on Day 4 of MW2's storyline. There's still plenty of mystery surrounding the exploits of "Soap" MacTavish and Gary "Roach" Sanderson (no word yet on whether Peter "Tucker" Jenkins will make an appearance), but by this point in the plot it seems that the gang are hot on the trail of a drug dealer named Rojas. At the start of the mission Roach and the other members of Task Force 141 are watching over a couple of Rio cops as they attempt to arrest a man named Faust - a subordinate to Rojas. Roach is keeping an eye on proceedings from the passenger seat of a nearby car, but it soon turns out that he won't be doing much sitting around today.

The two cops approach Faust as he leaves a building. Almost immediately he whips out a handgun and blows their faces through the back of their heads; seconds later another hail of bullets takes out the driver sitting next to Roach, leaving him slumped over the steering wheel. All hell breaks loose, but Roach is already out of the car with his weapon drawn. Captain Soap may sound like a brand of bubble bath, and Task Force 141 may sound like a failed boy band, but we know that these guys eat trouble for breakfast. It's a lesson that Rio's underworld is about to learn the hard way.

The first section of the level takes the form of a brief chase through the streets of Rio. Somewhat unusually for a CoD game, there's no direct combat here - although there's plenty of evidence of recent violence. As the player sprints after Faust we pass dozens of terrified civilians; most of them are screaming and cowering in fear; at least one of them lies dead in the road, having run into our quarry. Faust himself seems long gone, but as Roach rounds a corner we suddenly spot him climbing a flight of stairs. There are mere seconds before he'll escape, but that's long enough for a professional action hero to do his thing: Roach fires a few rounds into the fugitive's leg, and the screen fades to black.

When we fade back in, the action has jumped forward in time. Faust is tied to a chair and is about to be interrogated by Soap in true Jack Bauer style, with the aid of a car battery and some makeshift nipple clamps (well, a pair of jump leads). Soap sends Roach out into the favelas (slums) to look for Rojas with the help of two buddies - Meat and Royce. As the trio enter the shanty town, they fire into the air to scare away the local civilians; unfortunately this gunfire also attracts a the attention of Rojas' men, and a massive gunfight ensues. While the intensity of the action is pure Call of Duty, the gameplay here is given a slight twist due to the maze-like design of the map. Enemies seem to attack from all sides, and as Roach dashes from alley to alley it's easy to become disorientated - or at least it was for me, as a spectator.

We can't wait to play through the final game

The body count soars during this running battle, and indeed the death toll throughout the whole level is massive, even by CoD standards. The guy demonstrating the game clearly knew the stage like the back of his hand, and yet it still seemed like a marathon of bullet-based murder. If he wasn't reloading, he was shooting someone in the head or through a flimsy wall; if he wasn't doing that, he was ripping open a chest with a combat knife. And while Roach must take a good 20 to 30 scalps during this interlude alone, the gangsters also claim a prize: late in the fight, a report over the intercom informs us that Meat has just become Dead Meat.

As Soap extracts a location from Faust (who's probably had his balls burnt off by now), the action takes on a new vertical element: as the gunfight rages on, Roach and the surviving members of Task Force 141 must head deeper into the heart of the favelas, climbing through the housing blocks that line the hills of Rio. All the while Soap, and another colleague named Ghost, is shouting out desperate reports on where to find Rojas. Eventually we catch sight of the man himself: a slippery bugger with a backpack, clambering over the roof of an apartment. Roach has a clear line of sight, but an on-screen icon tells us that he's not allowed to shoot; Soap needs this one alive... if only for the time being.

All the time that this is going on, Rio's bandanna-wearing bad boys are doing their best to riddle Roach with lead - providing plenty of opportunity to see the grisly new blood-on-the-screen effect that pops up when you get hurt. Despite the odds, my demonstrator managed to steer Roach through the chaos without getting killed. The level peaks as we reach the very top of the slum district, affording a brief but beautiful view of Rio. The soundtrack builds to a crescendo while Soap and Ghost bark out frantic sightings of Rojas; it's all so dramatic that you might be forgiven for thinking the villain could get away, but - SPOILERS - he doesn't. Just when all hope seems lost, Soap rugby tackles him through a balcony and down onto the roof of a car, two storeys below.

It's a wonderfully overblown end to a blockbuster level. Though it goes without saying by now, Modern Warfare 2's campaign looks like it's going to be totally full-throttle - a rollercoaster ride of terrorists and explosions and action men doing ridiculously heroic things. It was impossible to avoid being sucked into Takedown's spectacular set pieces, but the graphical detail on display throughout was as equally impressive, if less show-stopping. At any given moment there seemed to be more stuff on screen, for want of a better word, than what we normally see in a game like this. Every location, every room seems to be packed with detail: bits of furniture, litter blowing in the wind, faded graffiti tags or cracks in a concrete wall.

Much of this is tiny stuff, and since you run past most of it with an AK-47 blazing in your hand, you may not even notice it at all. But the point is that it's there, and even if most players won't consciously acknowledge these touches, they'll most certainly have an effect on you as you play. This attention to detail is the scaffolding behind the scenes, the structure that supports the action movie insanity. Put those elements together, and you've got a Molotov cocktail of a game. November 10 is mere weeks away; is it time to get excited yet?

Call of Duty: Modern Warfare 2 will be released on PC, PS3 and Xbox 360 on November 10.