Splinter Cell: Double Agent is a game that puts Sam Fisher, a skilled agent of Third Echelon, in a new and challenging situation. His life has undergone dramatic changes, forcing him to work with his former enemies and find enemies among his allies. The story revolves around Sam's mission to infiltrate strongholds belonging to America's enemies, gather information, and neutralize threats to National Security. However, this time he is on the inside, working with those he has sworn to destroy, and risking everything for the greater good.
Players can experience the game in two different ways: stealthily sneaking around enemies or going all out with a gun blazing approach. The outcome will be vastly different every time the game is played, and there are three possible endings depending on the player's choices.
The game offers various weapons and gadgets to aid Sam in his mission, including electric, night vision, and heat vision abilities. These tools can be used to close lights, electrify enemies in water, or scan surroundings for potential gameplay objects.
This version of Double Agent differs from the Xbox 360/Windows release, adding a new single-player mission with an alternate ending, a new Spies vs. Spies online mode, and co-op multiplayer options. The Wii/GameCube versions only feature co-op multiplayer. The Spies vs. Spies multiplayer offers several game modes, including:
Deathmatch : regular matches.
Team Deathmatch : regular team matches.
Key Run : similar to Team Hack, but with the addition of a key that needs to be obtained first to hack into the opponent's computer.
Sam Vs. All : a single-player mode where Sam Fisher must sneakily hack into computers defended by an entire team.
Countdown : similar to Deathmatch, with the addition of gameplay time provided by killing other players.