HBO's In Treatment begins its second season just as Showtime's United States of Tara concludes its first. Both series are so engrossing, they prove that, in the right hands, TV isn't just good therapy. It's great therapy...

It only takes a few minutes of watching the new cycle of In Treatment to be sucked in totally, and to remember why this drama series, starring Gabriel Byrne as conflicted therapist Paul Weston, is so addictive. It's like a series of off-Broadway plays, or a flashback to those wonderful days of TV's Golden Age, when all you needed for riveting drama was a couple of people sitting around talking. The only thing that could make In Treatment more compelling would be if it were broadcast live.

The writing, acting and direction in In Treatment is so good, you're never aware of the acting, or the artifice. Even John Mahoney, the most familiar face as the unpretentious dad on Frasier, inhabits his role of a wealthy, anxiety-ridden CEO so completely, and so immediately, that you observe him as his character, not as an actor playing one.

And Byrne... does the word magnificent mean anything?

As with last season, In Treatment divides itself into five weekly installments, with a different patient given one of five 30-minute sessions. Unlike last season, these aren't parceled out once nightly, but in clumps, making it easier to stay current or catch up.

This season, the people interacting intensely with Paul are Mia (Hope Davis), whom he visits initially for advice about a pending malpractice lawsuit; April (Alison Pill), a college student with a secret so intense she writes it on a sheet of paper rather than speaking it aloud; Oliver (Aaron Shaw), a pre-teen boy whose parents are divorcing; Walter (the aforementioned Mahoney), a business executive with stress issues; and a weekly reunion with Gina (Dianne Wiest), Paul's mentor. You'll remember each, long after you turn off the TV.

HBO is making it easy to dive in. Even if you didn't see any of last season's shows, this year's batch gets you up to speed without stripping a gear. (Eventually, you'll want to go back and watch season one on DVD, but that's nothing but a big bonus.) And the scheduling, too, is easier to manage.

The first two installments, introducing Mia and April, are shown Sunday night at 9 ET. The next three, with Oliver, Walter and Gina, are shown Monday night at 9 ET, in a triple-header. And all five episodes of Week One are repeated Monday night, beginning at 8 ET.

What could be better? Not much.

"Every patient's therapy is different," Paul tells Mahoney's impatient Walter, who comes to Paul looking for an instant solution to his insomnia, and demanding guidelines on how his treatment is expected to proceed.

"Yeah, yeah, yeah," Walter replies grumpily, and very, very sarcastically. "We're all unique snowflakes."

Yes, they are, and In Treatment shines a light on each of them without letting them melt. One wonderful thing about this show is that it reveals its mysteries slowly, just as therapy would. Another is that while Paul is very, very good at listening, he's not without some pretty serious issues of his own. Both sides of the equation, in each show's dance of dialogue, is full of meaning and subtext. Even the silences speak volumes. Sometimes, especially the silences.

That's what's so satisfying about Showtime's United States of Tara as well. It's not only Toni Collette's performance as a woman whose consciousness occasionally splinters into various "alters" -- but that the reason for this schism has prove elusive, just as her family's attempts to accept her decision to forego her medication has been played for drama more than laughs.

Showtime presents the season finale Sunday night at 10 ET, so you can shift directly from HBO's In Treatment doubleheader and catch both therapy shows in one giant session. Or you can do the same on Monday: Watch all five installments of In Treatment from 8-10:30 p.m. ET, then jump to Showtime for the 10:30 ET repeat of Tara.

Either way, it's great therapy. And great television. Take full doses of both of these series, and thank me in the morning.