The sixth and final bullet forces its way into the gunman's chest, knocking him off balance and causing him to plummet from the roof of the house in a broken dive. I pause to reload my six-shooter, but my new friend, the home-owner, is still flapping about in panic. We've killed all the bandits outside, but there's still one bad guy inside the building - and he's got the landowner's daughter at gunpoint.

Back in the real world, a Rockstar rep is on hand to offer a spot of advice. As soon as I walk through the front door, I'll have just a few seconds to save the day. In a situation like this, it pays to be quick. In a situation like this, it pays to use Dead Eye - the Red Dead series' equivalent of bullet time. Time slows down, you run a reticule over the person you want to shoot, and targets are automatically painted over them; when you switch back to normal time, your unfortunate victim gets the Swiss cheese treatment.

Alright, I think. Let's do this! Under my digital command, John Marston enters the secluded prairie house. In seconds he spots the last remaining thug, holding a knife to the young woman's throat. And under my expert command... he runs into the side of the door frame like an enthusiastic drunk. The bandit makes a swift cut, slashing the girl's neck open. Swearing, I activate Dead Eye, and paint the sonovabitch with targets. Six little bullets riddle the murderer's body, and he collapses to the floor. The distraught father dashes in, begins to weep. I loot a chest in the corner of the room - and then, just for laughs, I loot the dead girl in front of her grieving dad. Hell, this is the Old West. You can't do the right thing all the time, can you?

This rather unfortunate episode was just one of the colourful moments I experienced while exploring the massive plains of Red Dead Redemption. To be honest, the sheer size of this game makes it quite a tricky proposition when it comes to writing a preview. There are so many side attractions and diversions here that I could easily spend the entire article focusing on these features - but then, that's exactly what I did in my last piece. No, today I'll resist the urge to tell you about the unexpected stuff - including a cannibal I found chowing down man-flesh in the middle of nowhere - and instead we can take a look at a few story missions.

A quick recap: RDR is the story of John Marston, a reformed outlaw who is dragged back into the world of violence by a shady government agency. The Feds want John to hunt down his old partner, Bill Williamson - and they aren't just asking nicely: the authorities are holding Marston's family, and they'll kill them if Williamson isn't brought in, alive or dead. The scene is set for an epic confrontation between one hard-as-nails man and his past, set in the dying years of The Old West.

There's a solid cover system in place

So, just as Niko Bellic spent much of GTA 4 attempting to find Darko Brevic, much of Red Dead Redemption will find Marston looking for Bill Williamson - and once again, this quest will force our hero to work alongside a whole host of slippery characters. In the first mission I was shown, Marston was helping a snivelling Mexican officer by the name of DeSanta - a weasely type who unfortunately has connections that Marston might be able to use. In this instance, DeSanta and his men are attempting to take back a stronghold that's been captured by Mexican rebels, a situation that requires you to battle your way up a winding slope and through to a heavily-defended outpost.

As you might expect, this assignment offered a great chance to get a feel for RDR's combat mechanics. As you might expect, there are a certain amount of similarities to GTA 4: there's a simple lock-on system for a start, and you're forced to make liberal use of a cover button, mapped to the left bumper (on the 360 version, at any rate). Gunplay feels fierce and chunky, but obviously your weapons have a slower rate of fire here than on the uzi-loving streets of Liberty City. As a result, individual bullets seem a bit more lethal, a feeling that is reinforced by the impact you get when you hit someone in a particular part of their body. While holding the left trigger will automatically lock you on to the nearest enemy, moving the right stick will allow you to manually tweak your aim. Guide the target over a man's arm, and you can cripple him; aim for his head, and you can pretty much guarantee and instant (and permanent) lights-out when you pull the trigger.

This first mission also demonstrated the game's sense of scale. As the Rockstar rep who was playing battled his way up hill, the whole game world stretched out around him. The fight itself took the form of a sort of marathon of violence, with Marston sprinting from cover to cover, opening up on Mexican rebels with his six shooter and a range of rifles - all of which can be selected using a simple radial menu. As the combat raged on and a dramatic Ennio Morricone-like score boomed over the soundtrack, Marston eventually reached a plateau in front of the fort. As the last of the rebels was finished off - with one man being shoved over the edge of a ravine - we were able to take a moment to admire the vista. From our raised vantage point we could see down to the camp where the mission began, while the surrounding landscape of Nuevo Paraiso stretched out all around us. It all looked terribly enticing, a world ripe for exploration and exploitation.

The second mission offered a slightly more intimate slice of action, and it also happened to be the first time that I got to take control of Marston for myself. This time things kicked off with a visit to a rugged-looking sheriff, a man who seemed to be well aware of John's past. A brief cutscene played in which the lawman detailed one of the problematic issues - or rather the problematic people - who were dogging his patch. Marston begrudgingly agreed to help, over the course of a gruff conversation that once again underlined Rockstar's commitment to production value. The scene itself wasn't a particularly spectacular event - it was essentially just two men having a short chat - but the gravelly voice acting of both characters worked as an excellent primer for the mission that was to follow.

The mission itself was relatively simple: ride out to the hiding spot of a local ne'er-do-well, and then either kill him or take him alive. The first part of this job gave me a good chance to get to know my horse. As you might expect from a Western-themed game, nags play a major role in getting from A to B, so it's no surprise to see that Rockstar has put a lot of effort into the equine NPCs. Put simply, the horses are brilliant: their movements look impressively realistic, they handle in such a way that makes you feel like you're actually riding something rather than the horse-shaped-car effect you'll often get in other games. They're smart, too. At the touch of the Y button you can whistle to call your ride over from wherever you left it, and when you're riding with an ally, as is the case in this mission, your steed will automatically match the pace of the people with whom you're riding. This last feature will be particularly appreciated by anyone who ever crashed their motorbike whilst trying to maintain a conversation in The Lost and Damned.

Once Marston and the sheriff reached their destination, I had a short battle with the villain's cronies before the man himself actually made an appearance. This seemed like an excellent opportunity to try out Dead Eye mode. Initially you're only able to slow down time when you activate this power, but at a certain point in the game you're taught how to queue up targets by painting your victims. This skill proves especially useful in situations like these where you're trying to take someone alive. Once our quarry had emerged from his shack, I paused time and lined up a couple of revolver shots for his legs; As play resumed, the bullets struck home and the bandit keeled over. Naturally, I could have just killed the man - but taking people alive will often lead to better financial rewards. Furthermore, your approach to jobs like these will affect your Marston's Fame and Honour levels. The first stat can only ever increase as your reputation spreads across the land, but the second value is more or less a karma system that affects how people respond to you. We still don't have a full picture of how this will affect the overall story, but it'll be fascinating to find out.

The world appears to be massive

My next job was the one I briefly alluded to at the start of this article. Given my piss-poor attempts at heroism I won't dwell on this too heavily, but I will point out that in the full game the whole experience would be entirely optional. Dotted around the game world you'll find certain locations that are just waiting to be stumbled upon. In this case, I came across a farm house which had been taken over by a gang. Close to the occupied home there was a terrified farmer begging for help, and as soon as I approached him a short cutscene triggered in which he explained the situation. There are obviously rewards to be had from lending a hand to the poor chap - or indeed to helping the gang members - but if I'd wanted to, I could have completely ignored him entirely. I'm not entirely sure what would happen if I returned to this spot later in the game, but I do know that your actions in these locations can be persistent. If you wipe out a gang hideout and come back a few days later, it'll still be deserted - and you'll probably see a few vultures circling overhead. It's even possible to wipe out entire towns, if you're feeling brutal - although they'll apparently re-populate after a certain period of time.

The final mission I sampled was another character-driven affair that once again recalled the spirit of GTA 4. Here Marston was working alongside a drunken character named Irish (no prizes for guessing his nationality). John had apparently saved this guy's life earlier in the story, and now the booze-hound was attempting to repay the favour by helping our man to find a fearsome gatling gun. Despite the fact that Irish seemed as reliable as a chocolate teapot, Marston had no choice but to follow his plans. The gun was being held at a nearby mine, so the two men set out for a spot of snatch-and-grab action.

In pure terms, this quest had a fairly simple setup: fight your way through to the objective (the gatling gun), then force your way out again. However, the setting of the mine itself offered a slight change of flavour. The winding corridors provided a claustrophobic contrast to the open-air shooting that had typified the rest of the demo, and this restricted space also seemed to make shotguns a more viable choice of weapon than normal. On top of this, Marston was also able to shoot down overhead lanterns - plunging the corridors into darkness and allowing him to creep up on his foes. In another improvement on GTA 4, it's no longer a sticky issue if you try to kill an enemy who's right next to you. Whereas Niko would struggle to hit foes in close proximity, Marston will automatically perform a set execution using whatever weapon he has at hand - and as an added bonus, these moves tend to be rather brutal.

Once the gatling was found Marston loaded it into a mine cart and proceeded to fire at the remaining miners one-handed as he pushed his new prize back into the daylight. By the end of the mission I was expecting everything to kick off, especially given how dodgy Irish seemed, but to my surprise he held up his end of the bargain, ferrying the gun away to safety on the back of a cart. Still, you can bet that the weapon will see some use later in the game, and I can't wait to see how that turns out. Gatling guns and Westerns make for a messy cocktail, as anyone who's ever seen The Wild Bunch will attest.

As I said earlier, there's a huge amount to talk about with Red Dead Redemption, and even after two previews I feel like I've barely scratched the surface in terms of the stuff there is to discuss. Still, that's probably a good thing, as there's going to be a huge amount of pleasure to be had in finding things out for yourself when the game ships later this year. We already knew that there were going to be loads of side missions and optional quests, but I'm pleased with the way the campaign appears to be shaping up. One often-voiced criticism of GTA 4 was that some of the missions were a bit too samey; Rockstar largely addressed this criticism with its DLC expansions, and it very much seems as if it's carried this varied approach over to RDR. In short, it's all looking pretty damn exciting - and we've yet to see anything of the multiplayer side of things. Time to file this one under "Most Wanted".

Red Dead Redemption will be released on PS3 and Xbox 360 on April 30 2010.