Claire Danes as Carrie Mathison in “Homeland.” (Joe Alblas/Showtime)

“Homeland” fans already know that the series is in for a necessary reboot when it returns Sunday night with back-to-back new episodes for its fourth season on Showtime. The old show and its old problems are not entirely wiped away — CIA agent Carrie Mathison’s life is destined to be a collection of loose and quite frazzled ends — but for the most part, “Homeland” feels more like the show it used to be: edgy, dour and violent in a way that can claim some ­quasi-relevance to international headlines.

True, Damian Lewis’s Sgt. Nicholas Brody is gone (if you’re not caught up to that point or don’t wish to know much about the premise for the first few episodes of the new season, then you should stop reading here), leaving Claire Danes as the television equivalent of a widowed star; in other words, the show now rests entirely on her.

Nicknamed “the drone queen” at her new supervisory CIA post in Kabul, Carrie seems somewhat even-keeled. A central theme in “Homeland” has been her struggle with mental illness, which she keeps at bay with proper meds and generous pours from the Chardonnay bottle in her fridge.

Acting on bad intelligence from a usually reliable source, Carrie’s team believes it has taken out a terrorist leader responsible for attacks along the Afghanistan-Pakistan border. In fact, the team has bombed a wedding reception. The ensuing outcry leads to another disaster, uploaded for all to see on YouTube — an ambush on an SUV carrying Carrie, Peter Quinn (Rupert Friend) and another agent.

Carrie is duly called home to Washington to account for the missteps. For the better part of an hour, “Homeland” is full of people telling one another, with the deepest antipathy they can muster, to [bleep] off. (“No, really, Carrie — [bleep] you,” Quinn sputters at one point.)

Still, the first three episodes feel like a step in the right direction. Brody’s end also meant the end (for now?) of story lines involving Brody’s depressing family, although, as Yoda used to say: There is another. Viewers will recall that Carrie was pregnant with Brody’s baby, and here she is, little ginger-headed Franny, fobbed off on Carrie’s long-suffering sister (Amy Hargreaves).

“Homeland” comes under quite a bit of criticism (some of it valid) from just about anyone with a working familiarity of Muslim cultures, but I’m surprised it doesn’t get dinged more often for explaining away Carrie’s worst traits as symptoms of her mental illness.

The more she acts like a male antihero (shirking parenthood for work), the colder we are made to feel toward her, and the more we lean on this idea that she’s not a “normal” woman. She’s become TV’s quintessential crazy ex-
girlfriend, rather than the complex character she once was. In one scene she tosses Franny’s baby carrier into the front seat, unsecured (the nation’s parenting bloggers just passed out), for a midday drive past the Northern Virginia house where Brody and his family once lived.

“You think I’m a bad mom,” Carrie tells her baby, gazing at the red-brick rambler. “I am. But he would have been even worse.”

Such moments of introspection are generally not “Homeland’s” forte — even though Friend, as Agent Quinn, delivers a terrifically wounded and edgy performance as his character suffers doubts about his profession and a dab of post-traumatic stress. Friend is doing more here than just acting as a Brody fill-in; “Homeland” could just as well be rebuilt around his character rather than Carrie’s.

Still and all, “Homeland” is better off when it shifts its narrative back to the season’s main story arc, in which “Life of Pi’s” Suraj Sharma plays Ayaan, a young medical student related to the terrorist targeted in the CIA bombing. (And yes, Mandy Patinkin is back as Saul Berenson, who is now a security contractor.)

The show feels new again, but that doesn’t mean it feels fully refreshed. Nor is it immune to painting itself into the same sort of corners it got stuck in before. “Homeland” also trafficks in some real-life context that is difficult to set aside at this particular moment in world affairs. These Islamic State beheading-video announcements — another of which occurred as I was filing this review — have production values that are in line with the storytelling techniques of “Homeland.” It’s as if terrorists in Syria have been pirating cable to make sure they get the scenes just right.

Homeland

(2 hours; double episode) returns Sunday at 9 p.m. on Showtime.