Set within a fictionalized version of the Chicago metropolitan area in 2013, the single-player story follows grey hat hacker and vigilante Aiden Pearce's quest for revenge after the killing of his niece.

[13] Aiden can scale vertical surfaces, hack forklifts and aerial work platforms to reach places otherwise unreachable,[14] and can crouch behind walls to hide from enemies.

Leaving Vega in the hands of his partner, hired fixer Jordi Chin, Aiden visits his sister Nicole and nephew Jackson for the latter's birthday but learns someone is harassing them.

Setting up a new hideout in the Bunker – an undetectable former Blume base with access to ctOS – Aiden tracks down the hacker with Clara's help: gang leader and Army veteran Delford 'Iraq' Wade.

To reach Iraq's servers, Aiden infiltrates a human auction he is attending to copy his access key, and blackmails his cousin Tyrone "Bedbug" Hayes into acting as his inside man.

Bedbug manages to obtain a data sample revealing that Iraq has information on almost every citizen of Chicago, protecting his gang from the authorities via blackmail.

As the data recovered by Bedbug is encrypted beyond Aiden and Clara's abilities, they decide to track down legendary hacker and former Blume whistleblower Raymond "T-Bone" Kenney, who caused the Northeast blackout of 2003 while trying to expose the dangers of ctOS, which he had helped to create.

Aiden, Kenney, and Clara are unable to decrypt Iraq's data because another hacker, JB "Defalt" Markowicz, infiltrates their system, steals it, and deletes it from their servers.

After dealing with Defalt and retrieving the stolen data, Aiden tracks down Nicole with Kenney's help and rescues her, allowing her and Jackson to leave Chicago for their safety.

As Kenney finishes decrypting the data, he informs Aiden of who ordered the hit on him: Irish Mob boss and Merlaut owner Dermot "Lucky" Quinn.

Unable to save Clara, Aiden makes the video of Washington's murder public, enraging Damien, who hoped to use the blackmail material for his own gain.

Kenney manages to track down Defalt, but while investigating one of his hideouts, he finds mannequins representing the people who died during the blackout he had caused eleven years ago.

Kenney begins to asphyxiate, but manages to hack the building's ventilation system through Frewer's phone, rerouting the gas to Defalt's room and seemingly killing him.

Beginning in 2009 with ten people and expanding to over a thousand,[25][26][27] Watch Dogs was developed over five years (from prototype to finished game)[28] on a budget of about $68 million.

The developer traveled to the city several times for field research, photos, recording audio, meeting people, and interviewing the Chicago Police Department to gain insight.

[35] The developers noted that character movements in games like Assassin's Creed were the same in every situation, and attempted to rectify this in Watch Dogs to contextualize protagonist Aiden Pearce.

[37][38] To create hacking factions in the game (like DedSec), the developer was influenced by the hacktivist group Anonymous, state-sponsored hackers, and tales of corporate espionage.

[36] Grand Theft Auto and Saints Row were studied to develop complex controls, so the core hacking mechanic was reduced to a single button.

[4] A QR code that appeared in the first gameplay demonstration as viral marketing led to a website called DotConnexion, which contained information about the in-game world.

[48][49] A free mobile app was released for iOS and Android devices, with Watch Dogs players connecting with console or PC users for two racing modes.

The expansion is separate from the main game and features ten story missions, as well as new side content and gameplay mechanics, such as an RC car.

[72] According to Ubisoft researcher Thomas Geffroyd, studies and quantitative analysis indicated that about sixty percent of gamers changed their view of technology after playing Watch Dogs.

[6] In Game Informer, Jeff Marchiafava wrote that the hacking added meaning to the combat, the shooting mechanic "make[s] full-scale firefights enjoyable", and praised the stealth approach.

[66] PC Gamer's Christopher Livingston called the hacking the game's most positive feature; although he liked the stealth, his favorite approach to battle was gunplay.

[67] For Polygon, Arthur Gies praised the combat's gunplay feature and wrote that it was "aided by a good, functional third-person cover system, which helps with more than just shooting — it also allows for effective stealth".

[68] Carter was dissatisfied with the story, citing "lifeless" characters and calling the plot's events "fairly predictable and clichéd"; the graphics were thought inferior to the game's marketing footage.

[16] Whitehead criticized the hacking for resorting to "tired old PipeMania-style" puzzles and saw the story and main character as the game's weakest aspects, saying that the script avoided the moral dilemmas offered by its set-up.

[67] Gies wrote, "After a promising (albeit well-trod) start, Watch Dogs' plot struggles to remain coherent", and likened the characters to caricatures.

[12] Tom Watson wrote in New Statesman that the game "has so many complex side missions and obligatory tasks that it becomes dull; it's humourlessly derivative of the open world of Grand Theft Auto V".

[75] It was the bestselling new IP ever in the United Kingdom in its first week (beating Assassin's Creed III's record by more than 17 percent), and was the seventeenth-largest game launch of all time in the UK.