A videogame franchise is a powerful and potentially profitable thing, but it is very much the double-edged sword: on the one hand there's a lot of money to be made from a successful brand, yet on the other, there's an ever-increasing expectation level that requires you to constantly better the previous efforts. Ubisoft's Xbox darling, Splinter Cell, has somehow managed to defy all expectations and spawn two sequels that not only pushed the envelope, they added stamps and a greeting card filled with goodies. Whether it was Pandora Tomorrow's incredible adversarial mode, or Chaos Theory's co-operative play that made you wish Sam always had a partner for his adventures, the development team's at Ubisoft never failed to disappoint with Splinter Cell.

So when Splinter Cell: Double Agent, the fourth game in the series, was announced last year, it led many to wonder what, if anything, the prestigious Shanghai and Montreal studios could do to top the combined pedigree of the Splinter Cell series. Rather than try and improve on perfect however, those clever kids at Ubisoft decide to take all the rules of Splinter Cell and throw them out the window. The result, in case you've been living in a cave with Bin Laden or can't read the subtitle, is that Sam Fisher becomes a double agent. His mission: infiltrate a domestic terrorist organisation hell-bent on deploying a weapon of mass destruction on US soil. His methods: well, read on!

Unlike previous Splinter Cell games, which had an overall story but often played more like a series of disconnected vignettes, Double Agent makes a concerted effort to weave the narrative, the player's choices and their consequences through every aspect of the game. Your adventure begins with a routine mission with Sam providing in-field training to a young Third Echelon cadet...things go pear-shaped pronto, and to make matters worse, Sam's old friend and mentor Irving Lambert breaks the bad news that Fisher's only child has been killed in a hit-and-run accident. This tragic thread does not recur during the game sadly; I think everyone would like the chance to unleash some Splinter Cell payback to the drunk-driver responsible. Nevertheless, the news breaks Sam's will to live, and the razor-sharp super-spy we've all come to know and love ceases to exist.

So Sam hits the turps and starts to self-destruct, and when Lambert comes to him with the most difficult mission ever presented to Third Echelon, one that involves infiltrating a terrorist group and becoming one of them, Sam doesn't even hesitate. The opening mission to Iceland was really just a playable tutorial level, and your mission proper doesn't begin until Fisher is thrown into deep-cover in the maximum security Ellsworth Federal Penitentiary. It's here that you'll get your first look at Sam Fisher in the cold light of day, devoid of his spy-suit and all of his gadgets. It's a chilling reminder of your new place in the food chain when your sole weapon is a home-made shiv that your new best friend Jamie Washington slips you. Armed only with this, your wits and a questionably sophisticated light/danger-detector on your back, you have to start a riot and help Jamie escape. It's a far-cry from the usual arsenal of guns and gadgets, but this is what makes Splinter Cell: Double Agent such a refreshing experience.

From the basic beginnings outlined above, Sam has to win Jamie's trust enough to earn an introduction to his shadowy masters within the domestic revolutionary group called John Brown's Army. Named after the first American Abolitionist to practice and preach open insurrection and violence as a means to end slavery, the modern-day organisation seeks to destabilise and destroy all that is wrong with contemporary America. But unlike John Brown himself, who led a few raids and killed a dozen or so people, these guys plan to use horrific weapons of mass destruction against civilian populations to get their point across. As ever, Ubisoft share the terrorism-duties and avoid vilifying one particular race, country or organisation, and conjuring the spectre of a well-organised and competent American militia is just as effective a bogeyman as Al Quaeda or other Islamic Fundamentalists.

This infiltration becomes key to your double agent mission, and introduces a new feature for the Splinter Cell series: trust. As detailed in Xbox World Australia's earlier preview, the trust system is a new dynamic that balances Sam's standing with both his NSA task-masters and the head of the JBA, Emil Dufraisne. In each mission, you will be presented with tasks and objectives for each group, often in direct conflict with one another. The NSA may want you to save on of their agents, for example, while the John Brown's Army need you to put a bullet in the spy. Lose too much trust with the NSA and Lambert will call off the mission and its game over, ditto for the JBA who will expel you from their ranks – or worse.

This creates a delicate balancing act that can be quite intense during missions, but unless you are playing on Hard difficulty (or you just plain suck!), it's pretty hard to lose enough trust with either group to bring about a sudden ending to your adventure. Rather, the fun comes from trying to keep both your bosses as happy as possible, which Ubisoft encourage by providing unlockable gear and gadgets if you complete bonus objectives for one side or another. In this way, Sam slowly reacquires his arsenal, which includes an array of grenades and mines of course, but also electronic lock-picks and advanced hacking tools to make your life simpler during missions.

Central to the trust system is the concept of choices – do you take the extra time to get info for the NSA, or do you hurry to meet Emil so he doesn't get suspicious? But the game goes two steps further by including choices of opportunity and directed-moments. When in Africa, Fisher witnesses civilians about to be executed, and he can either intervene and risk exposure, or stay on task and walk away. It's totally optional and does nothing to affect the game aside from granting you a bit more trust with the NSA, but it also encourages players to approach the game with their own sense of morality. This morality surfaces again with some truly tough decisions during the directed-moments; you've all no doubt seen or read about the moment when Sam has to decide to kill a hostage or refuse, but there's at least half a dozen other big moments like this in the game, and they can dramatically affect the outcome of your experience.

The other major new feature in Splinter Cell Double Agent is the inclusion of the John Brown's Army HQ as a central hub location. Their base, located in New York, is where Fisher spends his down-time between missions, interacting with his fellow felons, doing housework for Emil, and covertly gathering information, sabotaging plans, and placing bugs and listening device for the NSA, of course! When you first arrive, much of the HQ is off-limits to you, protected by an array of security including surveillance cameras, retinal scans, fingerprint locks, voice-recognition and regular human patrols to boot. Each time you revisit the HQ you will need to source a new form of access (voice, fingerprint then retinal scans) to get into the high-security areas, as well as use your newfound access to gather intel or place bugs. You can't get snap-happy either and break necks/spines or even use non-lethal takedowns, as this would blow your cover, so it's pure edge-of-your-seat stealth when you're on-base.

These infiltration interludes will no doubt be a love-it-or-hate-it addition to Splinter Cell gameplay, because it is quite a departure from the norm. People will talk to you, you have chores to complete, and Sam spends most of his time painfully exposed. At any given time you'll have anywhere from five to ten objectives to complete, and while most are optional, the timed-nature of these missions will only compound the stress for a lot of players. You have 25 minutes to complete your primary objective along with anything else you opt to do, and the various bonus and secondary objectives are a great way to get a quick trust-gain on both sides of the fence. For some reason, Sam can only walk around while out in the open and cannot jump or do anything remotely suspicious, which can make getting from A to B unnecessarily frustrating. But when you're sneaking into offices to trawl through classified documents, or lifting fingerprints from a sleeping man's night-table, these JBA Headquarters missions can be some of the most exhilarating in the game.

Which isn't to say: Double Agent's primary missions lack thrills and excitement, because there are some truly exceptional set-piece locations in this fourth Splinter Cell title. They're big levels too, often with wide open areas like the war-torn streets of Kinshasa and phenomenally detailed like the dizzying descent down a Shanghai skyscraper. The problem is that there isn't *many* of these missions at all, in fact, you've probably seen or read about pretty much all of them in screenshots or previews- there isn't a whole lot of surprises. This isn't overly detrimental however, because what missions and locations there are have been well implemented thanks to superb level design, and the fact that the missions all feel very connected to the story, which is great for continuity.

Continuity is one thing, but overall this is without a doubt Sam Fisher's briefest mission to date, weighing in at just ten missions (including the visits to JBA HQ), and a mere 8-12 hours of play-time depending on your skill and thoroughness. Of course you can always argue that a focused and more intense experience is better than a drawn-out snooze-fest, but it doesn't feel like there's a lot of meat on the bone here in terms of longevity. Die-hard Splinter Cell fans are the ones who will suffer the most unfortunately, because in addition to being short it's by far and away the easiest title in the series to date. Ubisoft have exhibited a dangerous pattern of simplifying (some would say "dumbing down”) their core Tom Clancy franchises, and if you felt that Chaos Theory's combat-loadout and forgiving gameplay sold the series down the river, then you'll feel like Double Agent has paddled all the way out to casual-gaming sea.

In a lot of ways, accessibility becomes the greatest danger for established franchises, and in a lot of ways, Splinter Cell: Double Agent feels like it is targeted at a new audience of casual players than it does at long-term fans of the series. Sam's repertoire of moves has been culled and simplified, which isn't necessarily a bad thing for a series that often felt like you had to remember too many tricky moves. The biggest sacrifice however is stealth, which has been boiled down to the bones for Double Agent. Gone are the independent light and sound meters, replaced by an overall danger and threat indicator. Green means you're in the dark or safely hidden out of sight, yellow means you're exposed or the enemy has heard/seen something and is alert, and red means you've been identified and that bad men with guns will be heading your way shortly.

Not only that, but it's entirely possible to play through the game without using the vast majority of your gadgets. Sam's goggles take a hit here; night-vision is still quite useful and the thermal goggles are kind of handy in the snow, but for the most part what was once an extension of Fisher's stealthy-self is now just a withered and useless appendage. Some of the unlockable goodies come in handy, but the fact of the matter is that the majority of players simply won't even want to use the bevy of grenades and similarly ham-handed noise-makers for what is supposed to be an exercise in discretion.

Really though, these are just the casualties of Sam's inevitable rise to blockbuster stardom, and overall Double Agent is a polished and thoroughly enjoyable experience. As always the voice acting is stellar, with Michael Ironside returning to bring Sam Fisher's character to life. The dialogue is good in Double Agent, although there seems to be less amusing conversations to eavesdrop on, and prompting captured enemies for more information beyond the first snippet of dialogue never really yields anything of merit. This time the soundtrack is scored by Behaviour, and while his tracks are good, they're nowhere near as memorable or fitting as Amon Tobin's effort for Chaos Theory. Elsewhere the aural experience is likewise good but not memorable – surround sound feels less well implemented in this iteration of the series, and there's less background noise in general. This, coupled with a few nasty audio bugs (the sound in the super-tanker level eventually just shutting off once the 360 gets sick of repeating the violent wind effects to name one), make the audio less impressive than in the past, but still miles ahead of many other games.

The visuals, on the other hand, are simply amazing, and much of this is attributable to the fact there's a lot more outdoor or daylight missions – the game is far less dark, and as a result, places where Sam is considered "green” and safe would in real-life be patently obvious to anyone looking in that direction. It's a concession to gameplay, and one that for the most part works because freefalling into Siberia or diving into the outdoor pool on a cruise liner is just damn good fun. Purists will take issue with these and a good many other things in Double Agent, but at the end of the day it's whether the game is fun that counts.

And Splinter Cell: Double Agent certainly doesn't fail there, it may be short but it's certainly sweet. The enemy A.I. on Normal difficulty is good but not great, although there's often a lot more NPCs in any given level than in previous Splinter Cell titles, which adds to the challenge. But the greatest challenge in the game comes in exactly the same form as the earlier titles: it's the targets you set yourself that truly shape your experience. If you want to go in balls-to-the-wall-guns-a-blazin' style you can, and you'll rarely be severely punished for it. If you want to play as a bad-ass terrorist you can do that too. Or, if you want to ghost through every level like a master ninja, then this is the game for you. More so than any previous Sam Fisher adventure, Splinter Cell: Double Agent is the experience you make it.

Of course once the dust has settled and you've enjoyed one of three very different endings, we come to the question of replayability. You can run through the game again on hard (which is far less forgiving!) or make sure you've collected all the JBA member profiles for an extra Gamerscore Achievement. But for most people, the next step – if indeed it wasn't the very first – is to tackle the game's multiplayer component. As is the Ubisoft way, this mode was handled by an entirely different studio, this time Milan and Annecy. And more than ever before, this division of labour shines through in a multiplayer component that bears only a passing resemblance to the main game.

The most important point to make is that the brilliant co-operative missions of Chaos Theory are gone, replaced with a much more pedestrian effort that is essentially a players vs. bots version of the adversarial multiplayer. As such, multiplayer is largely the same for the co-op challenges and versus mode, and involves up to six players (3 per side) in a capture-the-flag style game. The spies are tasked with downloading information from one of four terminals, and once complete, they must exfiltrate with the data back to their start location. It is up to the mercenaries to protect these key points and kill the spies. Exfiltrating with 2 sets of data is a win for the spies, and the clock running down or all the spies being killed is a win for the mercs.

Where Sam Fisher's awesomeness comes from his plausibility as a super-agent, the spies in multiplayer are unnatural little supermen who move like the road-runner and climb up walls and across pipes like Xenomorphs from the Alien movies. This is compensated by the fact they have no lethally offensive weapons unless they can get in position for a neck-snap. The mercenaries, on the other hand, are realistically slow to move, less agile due to all the body-armour and armaments, but ten times as lethal. Both sides feel unbalanced when you first start playing, but once you get a feel for each faction, this becomes less pronounced. Team-work is what really makes or breaks the experience; strike out on your own and you're likely to wind up dead.

The Annecy and Milan teams have obviously been charged with making multiplayer more "accessible” as well, and the result is a much less hardcore experience with a less steep learning curve. It's still a punishing and sphincter-clenching experience at times, but it's a whole lot easier for newbies to jump in and get their game on. Co-op challenges are essentially tutorials for this very purpose, and by the time you've clocked a bit of time with your friends, you're probably ready to go Live.

The game also rewards dedicated players with a vast array of unlockable content, ranging from new skins and suits (that can confer bonuses to health or stealth) through to flyby movies or concept artwork. Not only that, but your Gamertag retains your play experience and your unique spy and merc will gain levels and increase their skills, as well as any of the skins and suits you unlock. This encourages persistent play, though it also gives dedicated players yet another advantage over those who are just getting started.