By Mr. Ngaihte (19 Mar 2010)
The film begins with the armed forces getting a lead on a suspected terrorist. As the man is a recluse, getting a positive ID proves difficult, and the DOD's computer system recommends that the mission be aborted. From continued aerial surveillance of the area, the suspect is apparently attending a funeral but the possibility that it is a facade makes those present all nervous - the system continues to recommend abort. The Secretary of Defense (Michael Chiklis) agrees with the abort recommendation, but the President orders the mission be carried out anyway. This turns into a political backlash when all those killed turn out to be civilians, and retaliatory bombings are carried out in response.
The scene abruptly shifts to the life of Jerry Shaw (Shia LaBeouf), a Stanford University drop out who not only lacks any real direction in his life, but also faces great financial difficulty. He gets a phone call from his parents telling him that his twin brother, Ethan, is dead. Following the funeral, Jerry gets a $1,000 check from his dad. When Jerry tries to deposit the check and withdraw some money from the ATM, he's surprised to see that his account is filled with a lump sum of money. Soon he returns home to find his apartment filled with a large amount of weapons, explosives, and forged documents. He receives a phone call from an unknown woman, who explains that the FBI are about to apprehend him in thirty seconds and that he must escape. Not believing her, he is caught by the FBI, led by Agent Thomas Morgan (Billy Bob Thornton) and Air Force Office of Special Investigations Special Agent Zoe Perez (Rosario Dawson).
The unknown woman arranges Jerry's escape and has him join up with single mother Rachel Holloman (Michelle Monaghan). Holloman is being coerced into helping by the woman, who threatens to kill her son, Sam, a trumpet player on his way to Washington, D.C. from Chicago for a band recital. The woman helps the pair to avoid the police and FBI units, demonstrating the ability to remotely control virtually any networked device, such as traffic lights, cell phones, and even automated cranes. While Jerry and Rachel follow her instructions, the woman has a crystal explosive made into a necklace and its sound-based trigger placed inside Sam's trumpet. Jerry and Rachel are led to Washington, D.C. through various means. Along the way, they are introduced to the woman, who is actually a top secret super-computer called ARIA tasked with gathering intelligence from all over the world. ARIA, the overtaken computer, can control virtually anything electronic to that end. In light of the mistake made by the President at the beginning of the film, ARIA has decided that the executive branch is a threat to the public good and must be eliminated.
ARIA plans to destroy the President's Cabinet, and calls this Operation Guillotine. It has decided to leave the Secretary of Defense, who agreed with its recommendation to abort, as the successor to the presidency. She does not reveal this to Jerry or Rachel, merely explaining that she is trying to help the people of the United States. At the Pentagon, where ARIA is housed, Agent Perez discovers that Ethan worked as a technician for the computer and locked it down to prevent ARIA from carrying out her plan. Perez warns the Secretary of Defense and they discuss the situation in a sealed room to prevent ARIA from hearing their conversation. Jerry and Rachel arrive at the Pentagon and are led to the super computer, where ARIA forces Jerry to impersonate Ethan and use an override code allowing her to go ahead with the plan. She then instructs Rachel to eliminate Jerry to prevent the lock from being reinstated, but Rachel cannot bring herself to do it. Rachel is led out of the building by ARIA while Jerry is caught by Agent Morgan. Having been warned by Agent Perez, Morgan believes Jerry's story and takes him to the United States Capitol. On their way, however, ARIA sends an MQ-9 Reaper UCAV after them. Agent Morgan sacrifices himself to destroy the craft and save Jerry. Meanwhile, Agent Perez returns to the super computer and is successful in destroying it, but not before ARIA uploads roughly a fifth of its memory to another location.
Rachel is given the explosive necklace and sent to watch the President's speech. Sam's class, whose recital has been moved from the Kennedy Center to the Capitol for the President's State of the Union Address, begins to play. The trigger that will set off the explosive necklace is set to activate when Sam plays a high F on his trumpet corresponding to the word "free" in the last verse of the U.S. national anthem. Jerry successfully infiltrates the vicinity and fires Morgan's pistol into the air, stopping the performance and emptying the room, but provoking a Secret Service agent to shoot him in the shoulder. In the aftermath of the chaos ARIA caused, the Secretary of Defense urges that another super computer should not be built. Ethan posthumously receives the Medal of Honor while Jerry, injured but alive and well, receives the Congressional Gold Medal. The film ends with Jerry attending Sam's birthday party. Rachel thanks him for attending and kisses him on the cheek. She then tells Jerry that she is glad that he is there. After a second of silence, Jerry tells her, "Me too," and the film ends.