SPOILER ALERT: Do not read if you have not seen the March 26 episode of “Homeland.”

Carrie Mathison learns an important lesson in “The Flag House,” as Season 6 of “Homeland” heads into its final two hours.

Peter Quinn, Dar Adal, and President-elect Elizabeth Keane have flashier moments in the 10th episode of the season, but there are two big Carrie moments that are revealing about this most complicated character, limned to near perfection by Claire Danes.

For one, we get the extraordinary sight of Carrie Mathison telling the next president of the United States: “I can’t.” With her daughter Franny already a pawn of the larger conspiracy, Carrie can’t risk charging ahead with her plan to go on the record about CIA honcho Dar Adal’s past shortcomings as a way to stop his maniacal campaign against President-elect Keane. This tells us that Carrie took the words of her court-appointed counselor seriously two episodes back when he advised her to realize that her daughter has to come first in her life, at least sometimes. “My priorities shifted,” she tells Keane with grim resolve when the president-elect winds up at her Brooklyn townhouse.

But at the same time we learn that Carrie hasn’t given up her old CIA-trained reflexes. Toward the end of the episode, Saul finds Carrie’s personal Situation Room, with the familiar mosaic of newspaper clippings, printouts, Post-it notes, photos, and color-coded yarn stretched spread out floor to ceiling in her search for patterns and connections. Mandy Patinkin’s Saul smiles as he marvels at the thought process on display because he realizes that Carrie is still doing the investigative work she was born to do, even if she rebuffed his efforts to rejoin the agency early in the season. And even when he sees the Post-it that asks the ominous question: What About Saul? (Spinoff title!) This is probably an important set-up for Season 7.

“The Flag House,” written by showrunner Alex Gansa and directed by Michael Klick, has great touches throughout. Saul’s nervous walk through the famed diamond dealers row on 47th Street in Midtown is beautifully shot. The showdown between Keane and Adal is tense. Quinn’s return to an area of Queens where at least one diner waitress remembers him as “Johnny” is confounding, in a good way, challenging viewers to figure out the timeline of Quinn’s flashback in the titular safe house. The return of the great Sarita Choudhury as Mira Berenson is a treat.

Some of the dialogue is a little on-the-nose in an effort to reflect the issues of the day, but that doesn’t make the subject matter any less worthy of examination. And 
“Homeland” once again finds its storyline threading through headlines of the moment (Russian efforts to influence the U.S. presidential election, the Trump administration’s ties to Vladimir Putin loyalists, etc.)

“It’s not just about fake news and manipulating public opinion — it’s about stifling dissent,” Max tells Carrie of the real purpose behind the “social media boiler room” that he discovered last week. Dar Adal’s involvement in this scheme “violates about 10 federal laws,” Max declares.

“The Flag House” sets the table for the final confrontations to play out in the finale. But as we get to the end, it feels like this season’s central storyline is wearing a little thin. A new president wants to change the nation’s approach to protecting the nation from terrorism, and to take us off the war footing that has been the rule since 9/11.

Would a high-level CIA manager really go to such lengths to intimidate a president-elect just to ensure the status quo for the intelligence community? Would a right-wing firebrand like Brett O’Keefe be in league with said rogue CIA manager? Adal is painted to be as much of an ideologue as O’Keefe during his face-off with Keane. Hard to believe he could be a career CIA man under these circumstances.

Keane is duly alarmed by what she knows of Adal’s crusade. She’s completely Team Carrie-Saul now. “In the future, in case you’re wondering, this moment — right now — is when I decided to put your ass in jail,” she tells Adal as he drops his warning to her not to “go to war with your own national security establishment.” And that’s even before Adal directs O’Keefe to “weaponize” the unconscionable attack on the valor of her late son in combat. Elizabeth Marvel struts her stuff all across this episode. A lesser actress wouldn’t have been able to pull off her scenes with F. Murray Abraham’s Adal.

“Two hundred and fifty years of movement toward the light in this country. Toward justice. Say what you will, call me naive, but I believe in that light,” Keane tells a smirking Adal.

Here’s where things stand for the key players by the end of “The Flag House.”

Carrie Mathison: She’s grappling with Quinn’s apparent plan to take out Adal’s henchman, the burly guy who killed Astrid, was snooping on Carrie in Brooklyn and likely planted the bomb in Sekou’s delivery van. She’s also about to learn from Saul via Max’s cell phone video that Adal is in bed with O’Keefe. On the plus side, her chances of reuniting with Franny seem to be improving.

Saul Berenson: He appears to reverse his plan to skip the country after some tough love from Mira. He’s ready to fight back with Carrie and that crazy genius brain of hers as his most potent weapon. (We learn that Saul has had an escape plan in place, probably for years, with the orthodox Jewish owners of a New York City diamond shop who produce a tote bag with guns, passports, phones and money for Saul — plus a handful of diamonds for good luck.)

Peter Quinn: The most pressing concern for the show’s most damaged soul is the nasty chest wound that he’s still covering up. Even if there’s no bullet in there, he’s got to get to a doctor. Hopefully Carrie will realize this sooner rather than later as they sit in the dark looking at the burly guy through the scope of Quinn’s automatic rifle.

Dar Adal: He’s poked the flame-throwing bear and now it might flame him back. In Adal’s meeting in the boiler room with O’Keefe he sees Quinn’s picture on a laptop and seems genuinely surprised. Given what we’ve learned about Adal’s seduction of a young Quinn, this might not be pretty.

Elizabeth Keane: She’s overruling the advice of her communications team (sound familiar) and demanding to have a press conference to address the outrageous claims made in O’Keefe’s viral video. This can only be bad.

Max: The IT whiz with the heart of gold is probably heading to some kind of “Clockwork Orange”-esque torture chamber directed by O’Keefe’s Nurse Ratchet after the discovery that he used his phone on the boiler room floor. We also learn he has a last name! Sounded something like “Petrovsky.”