Sam Fisher finally infiltrates his fourth mission after a six month delay...

Quintessentially an Xbox franchise, despite its multi-platform appearances, Tom Clancy's Splinter Cell series has been key to Ubisoft's growing confidence in recent years. Sam Fisher is very much an established and easily recognisable videogame character now, thanks to his night-vision goggles and shadowy antics, and his annual counter-terrorist adventures have garnered a keen fanbase.

Set after the events of Chaos Theory, which certainly set the standard in the series when it was released in Spring 2005, Double Agent sees Third Echelon's most famous employee infiltrate a domestic terrorist organisation called John Brown's Army (JBA). Named after a real-life American revolutionary from the nineteenth century, the JBA is in the planning stages of something vile and unsavoury - which is where Sam comes in. The perfect candidate to infiltrate the JBA thanks to his emotional state after the death of his daughter by a hit-and-run driver, Fisher is a man on the edge. Sent to prison for robbing a number of banks (part of Third Echelon's plan to build a credible cover story), Fisher finds himself being recruited by a JBA operative called Jamie Washington whom he helps break out from jail...and so his time as a double agent begins.

For the last three instalments of the series, Splinter Cell veterans have been used to Sam skulking in darkened corridors, shooting out lights, and hiding bodies in shadowy places. In a bid to shake the series up a little and create a greater level of diversity, Double Agent finds Sam doing what he does best in a number of new situations including daylight missions, diving sequences, and incidental (barely interactive) cut-scenes. No longer hiding in the grounds of a Central Asian dictator's palace, Sam travels from the bright white landscapes of Siberia to the streets of Kinshasa; though missions such as the infiltration of Jin Mao Building in Shanghai remain classic Splinter Cell material. Of course being in the snow-covered landscapes of Siberia means that Fisher is given a white-coloured variation of his trademark bodysuit, whilst the mission on the Cruise Ship sees the operative don a John McClane-style dirty vest..."Welcome to the party pal".

Having missions take place in bright locations is a major departure for the series to date, and is set to offer something of a slight culture-shock for some players, as hiding in the shadows gives way to an emphasis on object-based cover instead. Other missions, most often in JBA HQ (which acts as hub in the game), even has Fisher without his trademark goggles, so between the new locations and the new Trust-based gameplay, Ubisoft certainly can't be accused of churning out the same old game.

Essential to being a good double agent is the ability to remain undetected by the target group and fulfil the objectives sent by your real superiors, in Sam's case, the US National Security Agency. Balancing Fisher's actions are two 'Trust' bars, one each for the NSA and JBA, with the primary and secondary objectives of every mission having varying effects on the level of trust that Sam enjoys. All of the mission objectives set in the game are optional to the point where one of the Trust bars reaches zero and the mission is aborted. One mission finds Sam ordered to plant a bomb onto a Mexican cruise ship by the JBA. Failing to do so will cause their level of trust in the double agent to drop to zero, but if player's do manage to accomplish their mission then they place the lives of hundreds at risk, something that the NSA would never allow (unless you're a conspiracy nut). Counter-acting the mass-murdering objective set by the JBA are a couple of goals released by the NSA: evacuate the ship by exploding a smoke bomb thorough the ship's air shafts, and obtain the radio frequency of the detonator so that it can be jammed before it goes off. Neither of the NSA objectives are mandatory to achieve (unless their trust in Sam is at a particularly low ebb), so it's up to the player's moralistic stance as these decisions are made through the course of the game.

The prospect of shaping the experience in such a manner is quite a compelling one, especially when you consider that Double Agent features a number of different endings depending on a player's actions throughout the course of the game. That said however, the ebb and flow of the Trust levels rise and fall like the tide, and there are times when player will find themselves stuck between a rock and a hard place. Unable to take the decision that's wanted because it would have too much of a detrimental effect on one of the factions, and lead to an all-too familiar Mission Over. As an alternative to the occasionally frustrating "trial-and-error" gameplay of its predecessors, the branching, self-determining gameplay isn't quite as developed or forgiving as perhaps it could have been. There are two escape routes built into the game that allow players to avoid being forced into particular moral dilemmas: one is an option that appears before a subsequent mission if one of the Trust levels is too low, giving players the option to go back and play through the previous mission once more; the other takes the form of time-based missions set by both the JBA and the NSA, taking place in the JBA HQ in New York City.

Following EA's example in the Xbox 360 version of Fight Night Round 3, there's very little on show in terms of a HUD in Double Agent. Light meters and health bars have now given way to a largely clear screen, with only the amount of ammo and the currently selected weapon onscreen permanently. Instead, Fisher now has a colour-coded light meter and alert system pinned to his back, which works well even when he's in prison! The meter becomes essential for even Splinter Cell veterans, because the gameworld's shadows don't seem to be as encompassing to look at compared to the past titles. Whereas dark corners and shadowy areas in Double Agent's predecessors were, well, dark and shadowy, it was easy to judge whether Sam was hiding effectively enough. In Double Agent however, you rarely feel that the darkness is as all-consuming as it perhaps should be. Sam's trusty NSA OpSat does however feature a wealth of information including updated objectives, a real-time 3D gameworld map, and background information on the main members of John Brown's Army. NSA gadgets are of course joined by Sam's trusty arsenal of Assault Rifle, Silenced Pistol, and accessories such as the Sticky Shocker, AirFoil, and various grenades. Unlike Chaos Theory however, players aren't given a choice of weapons according to the sort of infiltration method they'll use, and in that respect it's very much a return to the days of the original Splinter Cell and Pandora Tomorrow.

The level of artificial intelligence amongst the game's population is something that's absolutely vital in creating a convincing and immersive experience for Splinter Cell players. It's something that Ubisoft Montreal managed to implement with extraordinary success in Splinter Cell: Chaos Theory, and one of the reasons why that instalment is arguably the best to date. The sad fact is that even with the release of Double Agent, the AI of opponent characters has never been better realised than in Chaos Theory. All too often, AI-controlled characters seem to hear Sam breath from a thousand paces, whilst others are unable to see or hear him when they walk past his crouched body in semi-darkness. The inherent blindness and almost sixth sense like perceptions of enemies are just two examples of where AI falls flat in the game and threatens all too often to ruin the sense of immersion for players. There are also times when an enemy will spot Sam, begin to shoot at him and then seconds later drop any notion of checking various hiding spots - we even hid Sam in a metal locker in bright sunshine and in full view of a firing guard at one point, and the guard STILL didn't open the locker doors to find Fisher. It's really quite slack, and something that we wouldn't ordinarily expect to see in such a usually sound and well-rounded franchise such as this.