LOS ANGELES — Playing cocky charmers is a breeze for Blair Underwood.

But playing alpha male Alex, the ultra-aggressive patient on HBO's taut saga of psychotherapy, "In Treatment," is a welcome challenge for the 43-year-old actor.

"What's unique about 'In Treatment' is that you have a chance to be as raw and transparent and as intimate as possible on-screen," Underwood said recently during a chat at a favorite coffeehouse in suburban Studio City.

What's also unique about "In Treatment" is its nightly format. Each night, psychotherapist Paul Weston, played by Gabriel Byrne, sees one of five regular patients who return on the same night each week.

Appearing on Tuesday-night installments of the series, Underwood's Alex is a grounded Navy fighter pilot who has sought counseling after he bombed and killed innocent civilians in Iraq, then suffered a heart attack.

The clever Alex has played persistent head games with his long-suffering therapist, and their egos finally collide in their explosive fifth session airing Tuesday night.

"It's the juiciest stuff with Alex," Underwood said of his character's intensifying story arc over the coming weeks.

"When you first see Alex, you see all his posturing and confidence," Underwood said.

It's an attitude viewers may recall from Underwood's early days as brash young lawyer Jonathan Rollins on the acclaimed NBC series "L.A. Law."

"But 'In Treatment' is all about therapy," Underwood said. "Alex will be exposed. He'll be stripped to the core. ... And Gabriel is such a terrific actor that there's always a lot for me to play off of."

Executive producer Rodrigo Garcia cast Underwood as Alex after seeing him in the feature film "Madea's Family Reunion."

"I'd watched Blair for a long time on television — on everything from 'L.A. Law' to 'Sex and the City' — and he'd largely played likable characters," Garcia said. "But in 'Madea's Family Reunion,' Blair played an angry, dangerous, abusive character. He really was very frightening."

Underwood has a substantial list of TV credits, including a recent recurring role as Julia Louis-Dreyfus' boyfriend on CBS' "The New Adventures of Old Christine," plus stage plays and feature films. He has directed music videos, recorded the voice of Jesus for an audio Bible and produced a TV documentary on lottery winners for The Learning Channel.

Underwood also directed the upcoming movie "The Bridge to Nowhere," starring Ving Rhames, now in post-production.

"My drive is about creating opportunities to tell stories," he said. "Often the stories fall into the realm of African-American history, or characters that aren't usually explored on the big screen or on television."

Those characters include inscrutable billionaire Simon Elder, Underwood's character on ABC's "Dirty Sexy Money."

On the steamy adult soap opera, Simon has a murky agenda involving manipulation of the powerful Darling family. Simon's family once worked for the Darlings. And Simon was born in Russia.

"To play a character who's very worldly, who looks like me, that's what I'm drawn to."