On "Weeds," Nancy Botwin knows the everyday annoyances of modern life. Like, say, an anemic cell-phone signal when she needs to make a call.

But Nancy also faces challenges that aren't so routine: She and her cell phone are sharing the same room with five scary gangsters, each armed with a gun he's pointing at her head.

Worse: Nancy's hefty stash of marijuana — the object of everyone's concern — is mysteriously missing.

That was Nancy's plight when "Weeds," the offbeat Showtime comedy starring Mary-Louise Parker, ended its second season last fall. Now, with its return tonight, Nancy is right where viewers left her: under the gun (five of them, actually) as she tries to place her all-important call.

"It was a little bit tricky to find the mood again," says Parker when asked about picking up the same scene months after wrapping Season Two. "I had to work myself up into that same kind of froth."

A remarkable thing about "Weeds" is how funny it makes a premise that could be a real buzzkill: What you have here is a newly widowed mother of two who starts selling marijuana to maintain her family's comfortable suburban lifestyle. But increasingly that lifestyle is becoming Nancy's cover for a life increasingly committed to crime.

The soccer mom from picture-perfect Agrestic, Calif., "is a crook," says Parker, surveying the season ahead. "She's a gangsta!"

Witty writing (and an unforgiving eye for middle-class hypocrisies) deliver plenty of laughs. So does the series' primo supporting cast, which includes Elizabeth Perkins, Kevin Nealon, Justin Kirk, Romany Malco and newcomer Matthew Modine.

But "Weeds" is rooted in Parker's performance as Nancy, who, in her hands, is an anxious blend of boldness and delusion. Nancy stands up to the perils she has brought on herself, while going to great lengths to pretend they aren't there.

"I think her narcissism is offset by her naivete, to make her more palatable than she might otherwise be," Parker muses. "She's kind of a less ruthless version of Scarlett O'Hara: She's gonna survive no matter what, she's gonna make it work, she's gonna put on that red dress — you know, Scarlett puts it on and goes to the ball."

Asked if she began "Weeds" uncertain how Nancy should be played, Parker answers, "I liked the idea of finding a woman who would do what she did. I want to know what it is about her that we don't see."

Was finding her easy?

"I'm still trying," Parker says.

Nursing an iced coffee in a Greenwich Village cafe earlier this week, Parker is just a few days past her 43rd birthday. But she seems insistently a decade or two younger.

She describes herself as "a journeyman actor. I'm always looking for work." Seeking roles, she says, "that I can do something with."

She means something unencumbered by dialogue and stage directions printed on a page.

"I don't necessarily even READ the stage directions," she confesses with a saucy grin. "I black them out. Which can be bad. Sometimes, there's something there that's important.

"I'll be doing a scene and someone will say, 'Y'know, you hand the money to him now,' and I'll be like, 'I hand him the MONEY?' And they look at me and then turn to the director: 'She doesn't read the directions.'

"I don't want to just do what's there," she sums up. "I want to bring more to it. I don't want to do what's obvious. That makes me queasy."