Volatile CIA agent Carrie Mathison investigates and ultimately becomes obsessed with returned POW marine Nicholas Brody, who may or may not be an al-Qaeda-trained terrorist. Brody struggles to resume his domestic life with his wife and two children whom he barely knows. Saul tries his best to support his bipolar protégé while pursuing leads of his own and trying to hold his crumbling marriage together.
After missing and presumed dead for eight years, Marine Sergeant Nicholas Brody is rescued in Iraq, and returns home to his family. But CIA agent Carrie Mathison suspects he might have been turned by his terrorist captors, and believes he could be part of a plan to attack America.
Carrie continues to surveil Brody but is unable to follow his actions into his garage which is a blind spot, where Brody begins to perform an Islamic prayer. Meanwhile, Carrie receives visual confirmation from an undercover agent that shows Al-Qaeda member Abu Nazir on video meeting with the Royal Prince of the Kingdom of Saudi Arabia.
Brody prepares to enter the spotlight; Carrie closes in on an al-Qaeda plot.
The political powers that be make big plans for national hero Brody, but his increasingly erratic behavior threatens his media darling status; Carrie grows desperate for evidence linking Brody with Abu Nazir, as Saul directs her to focus on Nazir's money trail.
Brody confronts the lone survivor among the insurgents that held him, leading Carrie to believe she may be proved right about Brody once and for all - but Brody's reunion with his captor surprises everyone; the agency is hot on the trail of the lovers who bought a house near the airport with funds from a stolen necklace.
Reeling after losing key players in Nazir's plot against America, the CIA orders polygraphs on everyone who came in contact with them, including Brody, which Carrie sees as an opportunity to finally learn the truth.
The relationship between Carrie and Brody becomes more complicated when they head into the countryside for the weekend, while Mike and Jessica face the fallout of the truth about their relationship, and Saul catches Aileen on the run to Mexico.
As Carrie and Saul reel from the news that Walker is alive, the intelligence community clashes on the best way to capture him; Brody learns a shocking truth about his captivity.
After his attempt to sever ties with Abu Nazir, Brody finds himself reliving his captivity and recommits to his mission; Carrie finds herself in the middle of a public relations nightmare on the heels of the mosque shooting.
Carrie and Saul identify Walker's contact in Washington but their target has diplomatic immunity; Brody is approached to run for a disgraced congressman's seat in the House of Representatives.
In the wake of the explosion, Saul finds Carrie hospitalized and manic, but realizes her chaotic theories have merit; before his congressional campaign begins, Brody takes his family on a weekend trip to Gettysburg, where he retrieves an important item.
While Carrie is near catatonic and confined to bed, Saul investigates the unsettling implications of her timeline; Walker secures a perch for his mission; Brody makes his final preparations for the Vice President's policy summit at the State Department.