- "My name is Sam Fisher. I used to be a hero — now I'm a wanted man. I used to hunt terrorists — now I am one. I used to take orders — now I execute them. I've become... a double agent."
- ― Sam Fisher
Double Agent was released for the Xbox 360 on October 17, 2006. The Windows version was released on November 7. A PlayStation 3 version was released on March 29, 2007 and worldwide March 30, 2007.
Originally the game was set for a March 2006 release (coinciding with the release of Essentials), but Ubisoft moved the release date to September 2006 in order to have more development time. Ubisoft then released their fiscal quarter results for Q1 2006 and announced that Splinter Cell: Double Agent would be put back at least one month in order to boost Q3 2006 income.
The game begins on September 3, 2007 as Sam Fisher and rookie John Hodge are being flown to Iceland to investigate suspicious activities at a geothermal plant. After Fisher stops the missile launch after John was killed by terrorists, he is met by Colonel Irving Lambert aboard the V-22 Osprey to deliver bad news. Sarah Fisher, Sam's only child, has been killed by a drunk driver. Overcome with grief, he is unable to concentrate on his work and is pulled out of active service.
Shortly thereafter, Irving Lambert offers him the rank of a NOC (nonofficial cover operative), hoping that it will help him refocus. NOC's are operatives with backgrounds from both the CIA and NSA, trained to infiltrate organizations for HUMINT purposes. The government denies any involvement in their activities. The NSA stages multiple bank robberies and killings to set up Fisher to infiltrate a domestic terror organization known as John Brown's Army (JBA). He is sent to Ellsworth Federal Penitentiary in Kansas where he is placed in the same cell block as Jamie Washington, a JBA member, and begins digging a tunnel for escape. By February 2008, Fisher helps Washington escape and is welcomed into the JBA.
At their compound in New York City, Emile Dufraisne, the leader of the JBA, gives Sam the order to shoot Cole Yeager, the pilot of the helicopter used to escape the prison. If Fisher kills him, he will earn JBA trust and lose NSA trust. If he does not take a shot, Jamie will kill Cole and Sam will lose trust with the JBA. He is then sent on a mission to capture a Russian oil tanker in the Sea of Okhotsk. Sam needs to capture the tanker so Massoud Ibn Yussif, a JBA ally, can use it to deliver one of the bombs.
As soon as Fisher is finished, he is quickly flown to the Jin Mao Hotel in Shanghai. CIA agent Hisham Hamza orders him to record a meeting between Emile and a Pakistani nuclear scientist, Dr. Aswat. During the meeting, Aswat sells Emile several kilograms of Red Mercury, a fictional explosive material. With Third Echelon on high alert, Fisher is told to collect a sample from the safe in the meeting room. While he's doing that, Carson Moss radios in and orders him to steal Aswat's notes from his hotel room. The NSA then orders the assassination of Dr. Aswat.
With both the Red Mercury and Dr. Aswat's notes, the JBA constructs a bomb which they wish to test. Emile sends Fisher to Cozumel to blow up a cruise ship. The success of the bomb is determined by the player and is therefore the first of the three major events. Fisher can choose to either let the bomb detonate, maintaining his cover with the JBA, prevent the explosion by jamming the signal or framing Enrica by using her disarm code, if the player acquires it from her office during the JBA HQ mission. Jamming the signal makes player lose JBA trust, while framing Enrica maintains both NSA and JBA trust. In both of these cases, non-detonation causes Dufraisne to kill Enrica in a fit of anger. If the player doesn't have a lot of trust with the JBA and just disarms instead of framing Enrica, Emile will shoot Fisher and he will fail the mission.
Emile then goes to a meeting in Kinshasa with Alejandro Takfir and Massoud Ibn Yussif, allies of the JBA. Fisher bugs the meeting and finds out that the three terrorist leaders each have Red Mercury bombs. They plan to destroy Mexico City, Los Angeles and New York City. During the meeting, Hisham Hamza's cover is blown.
Emile orders Fisher to kill Hisham, who has fled to the Congolese presidential palace in Kinshasa, from the top of a radio tower with a sniper rifle. Fisher may shoot Hisham, but if he spares his life, another section of the level is unlocked where Fisher extracts him safely from the palace.
When Fisher returns to the headquarters, he is ordered to shoot Lambert, who was captured sneaking around the complex. The player can decide to either shoot Lambert or Jamie Washington with a Luger. Shooting Lambert will maintain the JBA's trust, while shooting Washington will send the JBA into high alert and reveal Fisher as a traitor. Lambert's final words to Fisher were reassuring him to do whatever it takes to disarm the bomb. Enrica Villablanca, if she is still alive, discovers Fisher's NOC status, but allows him to pass into the labs underneath the HQ, even giving him his equipment if he does not have it already.
Fisher proceeds through the compound, passing through the secret labs below. He observes Emile ordering his men to kill the scientists and prepare to detonate the bomb anyway. Fisher now has a small timeframe to disarm the bomb. After clearing the bomb room, and taking out Emile, Fisher disarms the device, preventing the disaster.
A SWAT team then storms the compound, crashing in through the ceiling. If Sam saves the cruise ship, CIA Agent Hisham and Lambert or only two out of three with NSA trust above 33%, then he evades capture, and escapes the compound, incapacitating a SWAT officer, and donning his stolen suit. In the unlocked bonus level, the NYPD pursues Fisher through New York, but he boards a stolen Coast Guard boat that Carson Moss is using to deliver the last bomb. Fisher kills Moss, disarms the bomb and escapes the boat seconds before it is destroyed. This ending is the only one that ends with "To be continued..."
If Sam only saves one out of three or two out of three with NSA trust below 33%, he is captured by the NYPD, charged with murder and conspiracy to commit terrorism, and pleads 'not guilty'. Before his trial begins, however, Sam breaks out of prison and is on the run. If Sam does not save any of the three or only one with NSA trust below 33%, he is initially captured by the NYPD, but escapes using a smoke grenade.
- Iceland Geothermal Plant — Geothermal Plant, 20 km from Akureyri, Iceland, 3 September 2007, 04:25
- Ellsworth Penitentiary — Ellsworth Federal Penitentiary, Kansas, United States of America, 1 February 2008, 23:04 EST
- JBA Headquarters - Part 1 — JBA Headquarters, Delta Atlantic Shipping Company, New York City, New York, United States of America, 2 February 2008, 16:27 EST
- Sea of Okhotsk — RSS Rublev, Sea of Okhotsk, 200 km off the Siberian coast, Russia, 5 February 2008, 05:18 Okhotsk Time
- Shanghai — Jin Mao Hotel, Shanghai, China, 6 February 2008, 23:03 Chinese Standard Time
- JBA Headquarters - Part 2 — JBA Headquarters, Delta Atlantic Shipping Company, New York City, New York, United States of America, 22 February 2008, 21:03 EST
- Cozumel — Cruise Ship, Cozumel, Quintana Roo, 27 February 2008, 10:14 CST
- JBA Headquarters - Part 3 — JBA Headquarters, Delta Atlantic Shipping Company, New York City, New York, United States of America, 28 February 2008, 10:56 EST
- Kinshasa — Kinshasa, Democratic Republic of the Congo, 1 March 2008 12:06 West Africa Time
- JBA Headquarters - Part 4 — JBA Headquarters, Delta Atlantic Shipping Company, New York City, New York, United States of America, 6 March 2008, 23:34 EST
- Coast Guard Boat — Coast Guard Boat, New York Harbor, New York, 6 March 2008, 01:02 EST
Fisher is given objectives from two separate parties, the JBA and NSA, sometimes forcing the player to choose between them in order to progress. Due to the fact he is "working" for two different organizations, Sam is faced with several choices in the game that affect his trust with the JBA and the NSA, represented by the "trust meter". Trust on either side affects Sam's weapon arsenal: completing NSA objectives will unlock a high-tech arsenal, while completing JBA objectives will unlock a lower-tech lethal arsenal. The complex weapon system in Chaos Theory is removed, but there are some new unlockable equipment. A non-linear storyline that changes based on the objectives the player completes (those of the JBA or NSA).
Multiple endings are introduced. The lock-picking mini-game returns and a new bomb defusing game is introduced.
Two alternate single-player missions, eight all-new merged versus and co-op maps and interactive cutscenes. Daylight missions, in which Sam does not have his goggles. Also, in the regular areas of the JBA HQ, Sam's only maneuver is walk. Regenerating health (a similar element was introduced in Call of Duty 2) and a simple three-state (hidden/exposed/alert) stealth meter, as opposed to the past light and sound meters. The PlayStation 3 version includes an, as of yet, unnamed female Splinter Cell; in the Xbox 360 version, she's available in a download by Xbox Live. The computer hacking mini-game returns and new mini-games are featured that let you decrypt e-mails and defuse bombs. A new type of level, where Sam has a little less than a half-an-hour to complete multiple objectives. He can choose what order to do them, and does not have to do all of them. The more you do for one side (or both sides), the more trust you can receive.
As part of the JBA, Sam must complete objectives set by them to gain their trust as well as complete objectives from the NSA. The decisions he has to make will become increasingly difficult as he progresses through the game. Earlier decisions, such as deciding whether or not to free all of the prisoners during the prison breakout, will just affect his score, but as the game progresses, Sam is faced with serious choices that could kill thousands if made wrong, but may blow his cover if he does not do it.
Despite this, Sam must make the JBA trust him, in order to gain access to the restricted areas of their base and complete NSA objectives. If he is seen in restricted areas before he is allowed to go there, it will dramatically affect his trust with the JBA. Similarly, if he is caught using an NSA gadget or picking a lock in JBA HQ, his cover will be blown.
He is also watched by the JBA in most of his missions, if he is seen completing NSA objectives or is thought to be doing something out of the ordinary, his trust will go down. Killing people apart from those ordered to be taken out will affect his NSA trust in the same way.
Engine-wise, the game uses an updated version of Chaos Theory, with improved animations for things you could do in Chaos Theory. The back-to-wall system has been generously updated, as Sam can now perform knockouts, kills, and grab characters from around corners. For example, Sam can wall-grab Emile Dufraisne or Carson Moss and interrogate him during the final parts of the game, resulting in a different scenario than the fight that ensues after grabbing them normally. Sam is also able to fire his pistol while peeking around corners, a feature that was missing from Chaos Theory. Sam can also move at full speed with his back to the wall, which is helpful in JBA HQ missions, because his walking speed is painfully slow unless his back is against the wall. Sam is also able to hide under, and inside various environmental entities, such as inside lockers, underneath vehicles and under desks.
Upon joining the game, the player selects one of two sides: the Spies of Third Echelon or the Mercenaries of Upsilon Force. The choice of side affects the player's mission objectives, equipment, and overall play style.
Third Echelon spies
The spies of Third Echelon are extremely fast and agile, much more so than the Mercenaries. The Spies have a variety of almost superhuman acrobatic maneuvers that allow them to navigate the map and infiltrate areas that their opponents cannot reach on foot.
The mission objective of the spies is to retrieve two encrypted files from four terminals scattered around the map. The spies use their wrist computer to hack the terminal. The closer the spy is to the terminal, the faster it can be hacked. All progress made whilst hacking any terminal is cumulative for that particular spy until he is killed, when the information will be lost. To win the game, the spy team must retrieve 2 files and return them to their starting point. The spy team can also win by killing all of the Upsilon Force members, but this method is risky and not advised. The whole mission takes place in less than 20 minutes, otherwise Upsilon wins the match.
Wrist computer - A powerful wrist computer with a range of ten meters which they can use to manipulate their environment remotely. While hacking, Spies enter a first-person view and can only change the direction in which they are looking, and walk. The wrist computer can turn off lights, break glass using ultrasonic sound waves, hack security doors, turn off the main electrical generator, and cause the mercenaries' EM vision and other equipment to malfunction.
Night vision goggles - capable of standard light amplification and infrared night vision, and thermal vision capable of sensing heat
Gadgets (capable of carrying one):
- Syringe - restores the health of the Spy or his teammates
- Flashbang grenade - blinds mercenaries for a short time
- Smoke grenade - creates a thick cloud of smoke that impairs a mercenary's movement and vision and can knock one out after extended exposure
- Jammer - can be dropped on the ground to create a fake presence on the mercenary's HUD
- Proximity Detector - always active device that detects the presence of a mercenary's within 10 meters, giving off a "heartbeat" style noise that gets faster as the spy gets closer
Upsilon Force mercenaries
The mercenaries of Upsilon Force are heavily armed with a variety of ways to neutralize intruders. They have a melee attack that knocks their opponents to the ground and temporarily stuns them. They have the ability to sprint for a limited period of time, reducing their turning and aiming accuracy. Mercenaries can also sprint into a spy, knocking them down and stunning them temporarily. They can rappel down certain surfaces, allowing them to move to lower floors quickly.
The mission objective of the Mercenaries is to defend the four terminals from attack by the Spies. The Mercenaries win when they kill all of the Spies or when the timer runs out before the Spies can successfully return two files. Mercenaries receive an audio and visual alert whenever a terminal is being hacked and also can see which Spy is currently hacking and how much of the file has been retrieved.
- Rifle - The Mercenaries have an assault rifle capable of fully automatic fire. The rifle has unlimited magazines and each magazine contains 40 rounds. It has a scope capable of 4x optical zoom for sniping.
- EMF Goggles - shows all electrically-active devices in the area, including a spy that is hacking or using night vision or thermal goggles
- Motion Sensor - always active device that outlines a fast-moving spy in white
- Torchlight - a flashlight attached to the mercenary's rifle
- Grenades - launched from the mercenary's rifle
- Drones - remote-controlled flying cameras capable of exploding
- Proximity Detector - always active device that detects the presence of a spy within 10 meters, giving off a "heartbeat" style noise that gets faster as the spy gets closer.
Mercenaries also have a visual aid to their detector, in the form of 3 concentric rings. Closer rings represent proximity while a dot in the center represents extreme proximity.
- Motorway 90
- Red Diamond
- Boss House
- Dawn Waves
- USS Wissdom
- Kinshasa (Console Exclusive)
- Secret base of the NSA (Console Exclusive)
The United Kingdom, American and Australian versions of the Official Xbox Magazine gave the Xbox 360 edition of Tom Clancy's Splinter Cell: Double Agent a 9 out of 10. The UK magazine said that it was "rupturing quality and oozing tension", calling it "stealth gaming of the highest calibre, full of imagination and augmented by an excellent two-way Trust system that leaves you pondering every choice you make and then having to deal with the consequences."
IGN gave the Xbox 360 version of Double Agent an "Outstanding" 9.0 out of 10, the Windows version a 9.0, and the PlayStation 3 version a 7.9 for degraded particle effects. TeamXbox.com rated it 9.1 out of 10, USA Today 9 out of 10, GameTrailers.com 8.9 out of 10, and 1Up.com a "Dynamite" 8 out of 10.
GameSpot gave the Xbox 360 version a "Great" 8.5, the Windows version a "Great" 8.0 noting "Some issues with stability and graphical performance", and the PlayStation 3 version a "Great" 8.0. The major difference between them is the level of online multiplayer, graphics and the controls which differentiates one from another.
GameSpy gave the Windows version 2.5 out of 5 stars, citing many bugs, inconsistent graphics, and high system requirements.
- Received IGN's award for Best Xbox Action Game of 2006
- Received IGN's award for "Best Original Score of 2006" for the Xbox 360
- Nominated by the Academy of Interactive Arts & Sciences for "Best Action/Adventure Game", "Best Male Performance", "Best Sound Design" and "Best Original Music" of 2006
- Won TeamXbox's "Best Action Game" and "Game of the Year" for the Xbox version.
- Won Gamespy's "Game of the Year" and "Best Action Game" for the Xbox version.
- Won Official Xbox Magazine's Action-Adventure Game of the Year - February 2007
- Won Official Xbox Magazine's Co-op Game of the Year - February 2007
The Soundtrack was composed and produced by Michael McCann (under the alias Behavior). McCann composed all music, except the Main Theme, which was composed by veterans Cris Velasco and Sascha Dikiciyan of Sonic Mayhem. Currently, anyone can download the complete score of both versions of the game from Michael McCann's website 
The Limited Collector's Edition of Double Agent was released alongside the standard edition. The cover had a plastic sleeve in which can reveal a transparent green tri-focal goggles. Inside the collector's edition contained the following:
- Behind the scenes feature
- Documentary on the realism of the game featuring a real life field operative
- MTV documentary on the game
- Interview with Michael Ironside
- Multiplayer Tips
- Seven mini-films
- Concept art gallery
- This is the first game that Sam heals by regeneration. In all past games, including Double Agent (Version 2), Sam needed a Medical Kit to heal. However, Sam is pretty vulnerable even on easy.
- While Double Agent features choice-based objectives as a crucial part of gameplay, it was not the first game to have this feature alone. The first game in the series to implement this feature was Pandora Tomorrow, but to a small extent. Double Agent expands on this feature by putting more emphasis on choice-based objectives that it would effect later levels.
- The first (and only) choice-based objective in Pandora Tomorrow was in the level "Jerusalem, Israel". After being escorted to a Syrian hideout, Sam had the choice to kill or spare Dahlia Tal before being met with patrolling policeman or Shin Bet snipers assisting Dahlia in eliminating Sam after retrieving a sample of ND133 near the end of the level.
- According to the game manuals and concept material from Double Agent, Sam is 5′10″. However, in cutscenes, Sam is taller than Lambert who is 6′2″.
- Female NPCs have a different animation when grabbed by the player.
- Some elements from Chaos Theory remains in Double version, most notably the guard's quotes, they are similar to the one used for Displace mercs.
- The Geothermal Plant level takes place on 3 September 2007 but upon arrival by helicopter and the station computers have letters dated late numbers, 14-18 September 2007. They contradict the mission date from the boot screen and state that level took place on 18 September or later. There are a number of these "future" emails throughout both versions of the game. For instance in JBA Headquarters - Part 3, set during 28 February 2008, there's an email about the armories from 5 March 2008 -- five days after the following Kinshasa mission that hasn't occurred yet. Version 2's JBA Headquarters - Part 1 likewise features a future email about "money from the train", a mission that hasn't happened yet, among other other future plot points and missions.
- During the final Iceland cutscene, Sam is wearing a completely different uniform, similar to the one he wears in the headquarters of JBA. Despite Version 1 of Splinter Cell: Double Agent being considered canon, the ending cutscene seems to fit more with Version 2 than Version 1. For example, Lambert aborts the mission in Version 2 which prompts Fisher to ask, "What's going on?!" while this reply doesn't make much sense in Version 1's Iceland mission (as the mission wasn't aborted). Interestingly, the cutscene's outfit matches neither Version 1's diving suit nor Version 2's classic suit. The opening cutscene for Ellsworth likewise matches Version 2 more as Sam is shown wearing the outfit from that version and the entire aesthetic of the prison, including the very cell that Sam is shown being shoved into, is nearly identical to Version 2.
- Despite having profiles in the OPSAT, it is impossible to obtain information for Hisham Hamza and Aswat.