SC:DA is Sam's most personal story yet. Whereas the previous ones "read" like a typical Clancy novel, Double Agent seems much more character-driven. After spending years with Sam, it is about time we get more intimate. As such, I found the story to be much more engrossing than the others. I hope this won't be a spoiler for anyone, but near the beginning of the story, Sam learns that his daughter Sarah, his most personal of relationships since the first game, had died. This, of course, has a big impact on him, and so he decides to take on his most dangerous assignment to date. He goes to prison in order to befriend a member of "John Brown's Army" (JBA), a domestic terrorist group, and infiltrate their organization. What I found interesting was how attached I became to this fellow prisoner; it's quite a job to escape from the prison and you have to depend on one another to survive. It's not like we were Red and Andy from The Shawshank Redemption, but I feel like we developed a bond that can only be shared by people who endure such trials together.
A similar comradery is created with Enrica Villablanca, the tech specialist of the JBA, who Sam says is not much older than his daughter. You go on numerous missions together and become closer to each other. Either rightly or wrongly, I find myself much more engaged with a story (such as this spy story) where the factor(s) at risk is much more personal to the main character than some bomb going off somewhere that's going to kill some large number of anonymous people (though there is that). I applaud the plausibility and cohesiveness of the previous Splinter Cell stories, but none matches Double Agent in terms of its engagement.
In terms of gameplay, Double Agent is a true successor to Chaos Theory, which Thrasher described as perfecting the Splinter Cell formula. DA continues to provide superior level design with multiple ways to go about overcoming an obstacle. Unfortunately, however, the mission rating system from Chaos Theory was not included (though I suppose, if you had the desire, you can use the stats given after you complete a mission and do the arithmetic: start with 100% and subtract 2% for each fatality you caused, 5% for every time spotted by an enemy, and so on). The game engine seems largely the same; I'm not certain if it is more forgiving in terms of the accuracy of firearms. One of the things I find most impressive is the fact that, four games in, DA still provides unique and interesting challenges. When in Kinshasa, you deal with the inconvenience of having an unreliable power grid: the lights are usually on and you have to time your moves with the shellings that knock out the power. When commandeering a tanker in the Sea of Okhotsk, enemies will try to capture and interrogate you. And, in a reversal of roles, one mission involves all the enemies having night-vision goggles. The best place to hide from them is where it is brightest. Upon completion of the game, for those feeling really hardcore, there is a difficulty mode that limits one's equipment to the goggles, knife, and EMP device. No stealth game will leave you feeling badder than Splinter Cell.
The defining distinction of DA is that in every mission, except for the first and the last, you are presented with opposing objectives from the NSA and JBA. You are given a one-dimensional meter of trust that is zero-sum between them: if you gain the trust of the JBA it comes at the expense of the NSA's trust. Obviously, the objective you select influences this meter. It also affects what cut-scenes you see and what equipment you will have for the missions. I very much like this feature, though I wish that it would more radically affect the direction of the story. Nonetheless, it adds replay value and more autonomy for the player.
What also should be mentioned is the fantastic co-op mode, returning from Chaos Theory. Completing missions truly requires teamwork and patience, but joy shared is double joy. This undoubtedly has become one of my favorite features of the newer Splinter Cell games (especially since I didn't spend enough time playing online to get good at that mode). Unlike other co-op modes, where you are basically playing the single player story with a friend, the co-op mode has its own unique levels related to the single player campaign. There are many obstacles that require synchronized effort with a partner: perhaps a ledge is too high and you need a boost, a camera has to be zapped as you sneak by, or a dual bomb requires two defusers. This isn't just co-op mode so that two players can play but a big addition to the core features.
Splinter Cell: Double Agent may be the pinnacle of the Splinter Cell series. It is the last game that features true stealth gameplay. We can only hope that the prodigal returns back to its roots (for more on this, see my post "Sad Day for Sam Fisher"). As for me and mine, we will be sticking with the classics until that happens.