Gabriel Byrne stars as therapist Paul Weston on HBO’s “In Treatment.” In the show’s second sea-son, which launched this month and continues tonight, Weston must deal with his own issues as he finds himself divorced from his wife and living alone in a new city.

When he was shooting the enthralling first season of “In Treatment,” Gabriel Byrne despised the chair he occupied when he was playing therapist Paul Weston.

Though this psychologically astute series is still addictive, in Season 2 some things have taken a turn for the worse. Weston, who has moved from Maryland to New York City, is enduring a series of personal traumas. And Byrne ended up with an even less comfortable perch, which he had to occupy for the five long months it took to shoot “In Treatment’s” second season.

“I didn’t like that chair last year, but I hate this year’s chair even more,” Byrne said in a recent interview in HBO’s New York offices, three days after shooting on Season 2 ended. “I said, ‘I want a chair that a regular therapist sits in,’ because they have to sit for all these hours all day. So they gave me this chair and it seemed comfortable, but it restricted my body movements even more. Before, I was able to use my hands and lean and do all that. I can’t do any of it this year.”

Byrne had already decided this year to eliminate Weston’s few props (eyeglasses, the occasional cup). And the restrictive nature of the hated chair served his goal, which was to “strip down” the character, who, at the start of the season, finds himself living alone, in a new city — stripped, in a sense, of his identity as a father and a husband due to his divorce from his wife.

“Now it really just is about his reactions,” Byrne said. “What I wanted was the camera to go inside, go into him and let the audience into his head. That’s kind of frightening, and very challenging. Because you don’t know” if the audience will follow.

It’s difficult not to follow Weston and his new array of patients this season, especially when the compelling Byrne shares the screen with seasoned actors such as John Mahoney, who plays Walter, an arrogant CEO suffering from insomnia, and Hope Davis, who plays Mia, a brittle Manhattan attorney who blames Weston, who treated her when she was in her 20s, for the problems that plague her two decades later.

The show, which consists of five half-hour episodes per week, has an easier-to-follow structure this season. Instead of showing episodes on five consecutive weeknights, this year HBO is airing two episodes on Sundays and three on Mondays. The first four episodes of the week depict Weston’s sessions with his patients, and in the fifth episode, he sees his own therapist, Gina Toll (the quietly masterful Dianne Wiest).

As was the case last year, there are suspenseful questions threaded through the season. The drama of “In Treatment” doesn’t just revolve around whether the patients will make breakthroughs and uncover difficult emotional truths, though those moments can be moving. And this year, Weston is also facing a lawsuit from a former patient’s father, who accuses the therapist of malpractice.

But to a great degree, the show is about whether Weston himself — a temperamental man capable of great stubbornness and even greater compassion — will be able to make sense of his life and stop punishing himself for his perceived sins.

Weston’s patients often fight his insights about their lives — and if there is any criticism to be made about this season, it’s that the new crop of patients can be a combative bunch, sometimes exhaustingly so.

But the irony is that Weston, who spends a good portion of his week engaged in verbal and emotional jousting with his patients, in his own therapy sessions sometimes battles Toll, who patiently deflects his occasional displays of defiance and arrogance.

“I think what makes him a good therapist with all his patients, and sets him on the right road, whether he says the right thing or the wrong thing — he truly listens,” Byrne said. “He may not have the answer, but he’s paid the person the compliment of listening to them.”

‘In Treatment’

When: 9 p.m. Sundays, and 8 p.m. Mondays

Where: HBO