The plot centers on a group of extraterrestrials, some of whom have been detained by the United States government for sixty-six years since their ship crashed in Alaska, while others have secretly assimilated among the general populace.

Since ninety-seven captured survivors refused to disclose information to the US, they were held in a nearby government facility, located on fictional Mount Inostranka.

The escaped extraterrestrials, upon learning of the CIA's plans, have mixed reactions: some want to try to salvage attempts to peacefully assimilate, while others want to fight against the populace.

Caught in the middle of these events is Sean Walker, whose plans to propose to his girlfriend Leila on a Caribbean cruise are cut short when she mysteriously disappears from the ship.

[3] After the pilot aired, he and executive producer Steve Stark answered some viewer questions on their Twitter feeds, one being the fate of the plane used in the assassination attempt, which ended up disappearing through a portal before it could crash.

"[6] Producer Steve Stark brought the original script to NBC in 2009, after hearing that the network was looking for an "event-type" series to add to its television lineup.

[19] The show appeared on NBC's development slate in early January 2010, when the network announced at the Television Critics Association presentation that it had green-lit production of a pilot episode.

[20][21] Casting announcements began in early February, with Jason Ritter landing the lead role of Sean Walker.

[22] In late February, Željko Ivanek was cast as Blake Sterling, and Ian Anthony Dale signed on as Simon Lee.

[38][39] Executive producer Evan Katz stated that "everything is designed to answer questions so you're not frustrated or feeling like we're making it up as we go along" and the writers intended to keep the viewers guessing in a "fair way.

Mary McNamara of the Los Angeles Times called it "as big, brash and promising as Heroes was a few years back".

[1] However, by the final episode of 2010 on November 29, the series had cut its audience by 46% and its demo rating by 48%, to 5.83 million and a 1.9/5 respectively,[69] although both of these were up noticeably from the previous week.

[79] Special features on the DVD include seven behind-the-scenes featurettes, six audio commentaries with cast and crew, deleted scenes, episode recaps, a photo gallery, and a never-before-seen look at Dempsey's back story.

[80] The Event has been syndicated for broadcast in several countries worldwide, including Canada where it aired simultaneously with the U.S.,[81] United Kingdom,[82] Ireland,[83] and New Zealand.