What happens in Vegas stays in Vegas… unless, of course, you're talking about a zombie outbreak. In that case, what happens in Vegas will slowly spread out across the surrounding area, re-animating the dead and resulting in thousands of painful deaths. Each chomped-upon victim will eventually turn into another shambling predator, a staggering corpse with an insatiable hunger for flesh. Sure, the military will eventually show up; when they do they'll eliminate any perceived threat that stands in their way - and that includes any poor sod who's taken a bite. They might stick you in quarantine, but more likely they'll just ventilate you skull with a few bullets, then drive off in a Humvee singing Minnie Riperton's "Lovin' You," in a strangled voice.
This is more or less the tricky position that Chuck Greene finds himself in at the start of Dead Rising: Case Zero. He's managed to escape Vegas, but on the way out his daughter took a bite, courtesy of Chuck's zombified wife. He's now trapped in the quiet little town of Still Creek, which is currently a little less quiet thanks to the presence of the hungry cadavers in the street. They moan, they stagger about in bad clothes, and they're stupid but dangerous - a bit like the audience of The Jeremy Kyle show. To escape Still Creek, Chuck will have to fix up an old motorbike by hunting down five missing parts; he'll also have to source some anti-zombification medicine for his kid, and perhaps rescue a few other survivors. Alternatively, he can just dress up in drag and spend the day chopping zombies in half with a big sword.
If this all sounds a bit familiar, it's because this scenario is almost identical to the one that Chuck finds himself in at the beginning of Dead Rising 2. The setting is different, but the basic gameplay - from the ticking real-time clock and limited saves to the endless toys and sandbox silliness - is practically identical. It's a clever ploy on Capcom's part: create a bonsai replica of the full game, throw in a few cross-over bonuses (XP and cash earned here will carry over to future Dead Rising 2 saves) and then sell it at a low price - a measly 400 MS points.
You might argue that Capcom are effectively charging people for a demo, and that this is a bit cheeky when we're all used to getting such content for free. This is essentially true, but rather than being a cut-down version of a forthcoming release, Case Zero is a custom-built scenario that ties into the plot of the true game; it's essentially a piece of DLC that's been released before the main course, rather thank after it. More importantly, it offers a commendably large bang for your buck.
Perhaps the most impressive thing about Case Zero is the fact that it plays out almost exactly like a miniature version of the Dead Rising experience. It's not a single mission, or truncated slice of something larger: it's a full scenario, complete with side quests, multiple endings, and the endless temptation to mess around with the tools and weapons at your disposal. The core quest will take a couple of hours to beat, but due to the nature of the game it's highly unlikely that you'll get the best ending on your first attempt.