In the year 2019, Chicago is placed under martial law after extraterrestrials invade across the globe. The Drummond family is attempting to flee the city but every exit is barricaded. After breaking through an uncrewed barricade, their car stops inside a tunnel where extraterrestrials are waiting at the other end. Before they can reverse, the aliens attack, vaporizing the father and mother in the front but leaving their two sons alive in the backseats.

By the year 2027, the world has capitulated to the invaders and submitted to their governing authority. They call the aliens "The Legislators" because all subsequent laws and rules of governance come from them. In the years after Earth's surrender, the aliens have conscripted humans to build suitable habitats for them far underground called "Closed Zones", walled off from the rest of the city with access only granted to high government officials.

Gabriel Drummond (Sanders), the younger son from the opening scene, lives in the impoverished neighborhood of Pilsen. He is confronted by Chicago Police Commander William Mulligan (Goodman), who was partners with Gabriel's father before the invasion. Mulligan is convinced that the resistance group called Phoenix has not been neutralized, contrary to what the public has been told. Gabriel has no information to give and refuses to snitch anyway.

Later, Gabriel meets with a member of Phoenix to sell a hand-rolled cigarette containing secret information that he received from a coworker. The man takes him to Wicker Park, where he meets his brother Rafe (Majors), the leader of the resistance. Rafe takes the coded cigarette and directs Gabriel to leave the area because Phoenix is planning an attack at the upcoming Unity Rally at Soldier Field. Gabriel rushes to his apartment and hastily begins to pack. As he leaves the apartment, he is again confronted by Mulligan, who had surveillance on him. Gabriel evades Mulligan and hides underground.

The hand rolled cigarette given to Rafe contains a code that allows Rafe's team to access the Special Branch's surveillance system and see where certain individuals are, including their target, as well as deployment patterns for security. Rafe and other Phoenix members attack the Unity Rally, using an invisible alien explosive device against the alien guests when they arrive. The attack initially appears successful, but the city is immediately locked down and law enforcement swarms the city to locate the attackers. The aliens, angered by the attack, bring in hunters from off-world to seek out the perpetrators. They quickly zero in on Rafe and his accomplices Anita (Caitlin Ewald) and Daniel (Daniels). Anita is vaporized when she attempts to rush one of the hunters and Daniel ingests cyanide to avoid capture, but Rafe is shot and arrested by Mulligan before he can take his cyanide.

Gabriel emerges from hiding but is later taken into custody during a police raid. Mulligan shows him his brother being tortured for information and convinces him to send a message through the Phoenix communication network in hopes of meeting Number One, Phoenix's supposed ringleader. He is eventually led to Jane Doe, a prostitute who runs a brothel in Pilsen. She acknowledges him by name when he arrives, confusing Gabriel, and at that moment a police strike team raids the house and kills Doe.

The subsequent investigation reveals that Doe had bugged her own residence to record conversations with members of Special Branch whom she had serviced, to glean classified information. The tapes reveal that (framed) Police Commissioner Eugene Igoe (Dunn) divulged sensitive information about the aliens's arrival to Soldier Field which allowed Phoenix to develop their attack strategy. Igoe, along with Rafe and many others, are deported off-world and Mulligan, declaring the Chicago threat neutralized, is promoted to Acting Commissioner.

Mulligan later meets with Gabriel privately, with Gabriel lamenting that Rafe's plan failed. Mulligan, retrieving a box he received from Doe in an encounter earlier in the film, opens it to reveal a BlackBerry phone inside. He removes a memory card which he turns over to Gabriel and suggests that failure was the plan all along. Gabriel takes the card from Mulligan, and reviews the contents ? a video depicting his own baby shower years earlier, before the invasion, where Jane Doe is revealed to have taught at the same school as Gabriel's mother. It was at the shower that they were introduced to Mulligan. Several members of Phoenix were present at the shower and the video closes with Mulligan leaving a kind message for Gabriel inspiring him to carry the torch of Phoenix.

Meanwhile, Mulligan is cleared to go underground and meet with The Legislators in their habitat. As he descends, the same invisible substance that made up the powerful alien explosive used in the attack at Soldier Field is seen enveloping him, indicating he is part of the resistance and the plan was orchestrated to get him close enough to deal a fatal blow to The Legislators.

During the credits, a map details that the Closed Zone was indeed successfully destroyed, and that several other resistance strikes and protests have broken out in cities all over the U.S., Asia and Europe, indicating that the opening exhortation to "spark a match and ignite a war" has come to fruition and humanity is overthrowing their alien oppressors.

https://en.wikipedia.org/wiki/Captive_State
Sinon