Watch Dogs follows a man that can control the electrical grid of the city of Chicago. He has mobile hacking technology, which allows him to match people's real life identities with their online presences; as well as this, he can shut down mobile phone reception and listen in on phone calls.
Players can also take on the roles of the titular watch dogs, protectors of Aiden Pearce, as he is chased by police. Multiple players exist in the city at one time, although when this multiplayer triggers or what other players would be doing when Aidan is not in trouble is unclear.
In 2003, a disgruntled employee at a New York power plant secretly planted a virus in his company's computer system, which led to a massive blackout that disrupted power and communications to the entire northeastern US, resulting in hundreds of injuries and even a small number of deaths. 10 years later, a system called "CtOS" (Centralized Operating System) has simplified these connections, connecting entire cities in one gigantic network. The computers that run the CtOS are corporations interested in collecting the massive "data shadows" of every person, for uses from selling products to influencing worldviews.
While the CtOS makes such connections easier, it is only a matter of time before someone figures out a way to hack into this network and use or abuse it to suit their own purposes, and when that happens, the damage could be even more catastrophic. Enter the "Watch_Dogs," who seek to exploit this network, though their motives are unclear.
When the game was announced at the Ubisoft E3 2012 conference, a lengthy gameplay demonstration was shown. In this demonstration, the protagonist is shown controlling the electricity grid, which allows him to manipulate street lights. This power was used to create a pile-up to entrap a digital artist named Joseph Demarco. Another section of the demo shows him trying to gain access to a building. In order to distract the guard at the door he shuts down communications in that area of the city at which point calls are cut off for NPC's. This causes enough confusion that the guard effectively abandons his post and allows the player into the building.