The theme music may be “Little Boxes,” Malvina Reynolds’s great 1960s song about small-town conformity, but nothing about “Weeds” conforms to anything you’ve seen before on television. The citizens of Agrestic, the California cul-de-sac where this terrific new Showtime series is set, don’t behave the way you expect them to; in fact, they don’t behave at all. The city councilman has an unabashed passion for pot and porn, and his dealer divides her time between baking marijuana-laced desserts for her customers and dealing with the stresses of single motherhood. The neighbors don’t suspect, quite possibly because they’re too stoned to notice. The entire community seems happily enveloped in a cloud of tasty smoke.

Yet it’s the sober and realistic storytelling in “Weeds” that makes this mandatory television in a summer crowded with brat camps and dance contests. The woman behind “Weeds” – a young television comedy writer named Jenji Kohan – has worked diligently to design a series meant to be sucked in slowly. It takes a few episodes before you realize “Weeds” isn’t about marijuana at all; it’s a character study of Nancy Botwin, a woman in her late 30s who’s trying to define herself without a man in the middle of her life. Her husband has recently died, and she has two young boys and bills to pay, but she refuses to depend on anything except her own resourceful nature to get by. Her decision to deal marijuana to the neighborhood stoners seems less a crime than a pragmatic act to save herself.

The gifted actress Mary-Louise Parker, working at the top of her game, has made Nancy Botwin into the kind of multidimensional woman most television executives fear – maybe because she doesn’t need a man to “complete” her life. It’s impossible to think of a woman on television who doesn’t somehow depend on a man to shape her existence, or define her role; even a strong female character like Carmela Soprano lives in the shadow of her even more powerful husband. Much of the fun of “Weeds” comes from seeing Nancy cope – diving under her SUV. when she thinks she’s being shot at in a drug raid, delivering pot-laced baked goods to a poker game to drum up some quick cash, or driving around Agrestic in a beat-up pimpmobile after she’s forced to give up her car to her supplier. She keeps her family afloat on the wad of cash she keeps stashed in her purse.

The people of Agrestic (a word the dictionary defines as “uncouth”) hardly act like your typical suburban television types, either – especially Nancy’s friend Celia, played by Elizabeth Perkins, whose sexy daughter sleeps with Nancy’s older son Silas in episode one before shipping off to Mexico, and who responds to her husband’s extramarital affair by shaving his head in the middle of the night. Former “Saturday Night Live” star Kevin Nealon turns up as Nancy’s best customer, a pothead public official who will stop at nothing to score the finest smoke. In the fourth episode, Nancy’s wayward brother-in-law Andy arrives to move in with the Botwins for a while, but just when you think the producers have caved to commercial demands for a male around the house, you realize he’s only there to give Nancy another child to take care of. Actor Justin Kirk (best known for his Emmy-nominated performance in “Angels in America”) delivers an effortlessly freewheeling performance as Andy; when he enlists Nancy’s younger son Shane in an effort to hawk hundreds of sacrilegious T-shirts to his schoolmates, it’s less an act of political incorrectness than the sort of stoned behavior that keeps Agrestic humming.

The main weakness in “Weeds” comes from the show’s insistence on drug dealing as a harmless vice. Nancy’s drug supplier – an overly jovial black woman named Heylia who never leaves her kitchen table full of buds and baggies – seems far too benign and sympathetic for someone who sells pot by the pound. Aside from a first-episode nod to Nancy’s policy against selling marijuana to children, little is said about the moral questions raised by the occupation of the central character, even if she is doing it for the noble purpose of feeding her family. While it’s true that “The Sopranos” at times veers dangerously toward making its characters overly appealing, it brings us back to reality with frequent and brutal acts of violence. It would add something to “Weeds” to remind us more frequently of Nancy’s fragile and corrupt moral universe, and the real dangers involved in a life of criminal enterprise.

Still, it’s a joy – and no surprise – to see Ms. Parker so effortlessly pull off the role of a lifetime; she has long been a luminous New York stage presence, and regularly coveted by television producers to star in her own network series. By waiting for “Weeds” – perhaps by seeing in Nancy Botwin a mirror of her own experience as a single mother – she has made Showtime a destination point on Sunday nights at last. With more attention to the deeper issues raised by this fascinating and addictive premise, “Weeds” could grow to become a show of female empowerment like no other on television.