"Monk" see, "Monk" do.

Three seasons as phobic detective Adrian Monk have left actor Tony Shalhoub in a slightly similar state of obsessive-compulsive disorder. Human contact sometimes prompts a germ of an idea. A picture hooked crookedly can also unnerve him.

"I never had a problem shaking anyone's hands before. But now I have that horrible little thought going through my head," Shalhoub says in a telephone interview. "I wish I could get rid of that. And I find myself bothered by things that aren't exactly straight. I think the compulsion is kind of growing in me."

Still, the veteran actor is enjoying the fruits of full-blown success after a second-banana stint on NBC's "Wings" (as cabbie Antonio Scarpacci) helped springboard him to what likely will be his lifelong signature role. "Monk," returning for a fourth season tonight, remains the highest-rated series in the 25-year history of the USA cable network. It has won Shalhoub both an Emmy and a sometimes manic "Monk" following.

"People talk about 'Monk Moments' and 'Monking out,' " he says. "I try to stay off the Web sites where they kind of deconstruct every moment and obsess about the show. I'm glad that people are feverish about it, but for me, it's healthier to keep a kind of distance."

USA again has ordered 16 episodes of "Monk," which will be served in two doses. Some fans were confused by last season's split shift and the sudden departure of Monk's loyal assistant, Sharona Fleming, played by Bitty Schram. Here's how it went:

Season 3 started on June 18, 2004, with nine episodes shown through Aug. 20. Then "Monk" vanished until Jan. 21, as did Sharona. The show resumed with Traylor Howard ("Two Guys and a Girl") cast as Monk's new ally, Natalie Teeger. What happened to Sharona? For Monk's purposes, she had moved to New Jersey to remarry her ex-husband.

The off-screen story is that Schram wanted more screen time.

"It was kind of a mutual thing," Shalhoub says. Schram "had become kind of disenchanted with it and wanted to pursue other things. So it was time for a change. ... We had a really difficult time finding someone who was not the same as Sharona and yet still had the same kind of vibe."

Shalhoub sees a bright side to "Monk's" truncated schedule.

"I think people are getting a little more used to it," he says. "The advantage of airing them in two blocs is that viewers don't have to wait as long before new episodes come along."

Tonight's Season 4 opener features an engaging guest appearance by Jason Alexander, whose rumpled detective, Marty Eels, keeps one-upping Adrian Monk during a murder investigation.

There's also talk of a "Monk" feature film.

"I'm having the time of my life," Shalhoub says. "I can't imagine a better scenario for myself right now."