NEW YORK – Gabriel Byrne spends much of his new drama planted in a chair, engaged in dialogue with whomever occupies the sofa facing him. He has plenty to say, but what distinguishes his performance is something else he must do: express the act of listening.

“I found it very challenging,” says Byrne, “to play a character who has to listen.”

Byrne plays Paul Weston, a busy psychotherapist. The series, HBO’s “In Treatment,” is built around sessions with a round of clients who challenge Weston and, maybe, drive him a little crazy.

“In Treatment” is an extraordinary drama, and not just thanks to Byrne. With an ambitious structure likely unprecedented on American TV, it unwinds in half-hour episodes, Monday through Friday, for nine weeks – with each weekday’s instalment featuring the client or clients who routinely see Weston that day.

Premiering in Canada Monday at 8:30 p.m. ET on The Movie Network and 9:30 p.m. PT on Movie Central, the series finds him meeting with Laura (Melissa George), a beautiful young anesthesiologist who wants more from Weston than therapy.