Last Christmas, as Mark V. Olsen screened a new episode of "Big Love," the HBO drama about a suburban polygamous family that he created and produces with his partner Will Scheffer, he found himself deeply unsettled.

The actions taken by the Henrickson family to protect their way of life — measures that seemed so palatable in the script — had a different veneer when Olsen viewed them onscreen.

"I couldn't tell what I was watching," he recounted. "Is it a cult at work? Or is this a loving, valid family? It was very disturbing to me. But at the end of the day, I kind of like walking that line and letting the audience make up their own minds."

The fact that "Big Love" keeps even its creators guessing about its true intent speaks to the subtle workings of the series, which returned for its second season on Monday (and airs again tonight at 5:30 p.m.).

The show hinges on the relationship between Bill Henrickson (Bill Paxton) and his three wives — levelheaded Barb (Jeanne Tripplehorn), wily Nicki (Chloe Sevigny) and impulsive Margene (Ginnifer Goodwin) — whose arrangement is at once startlingly unorthodox and staunchly traditional.

The founder of a home improvement store chain, Bill frets about keeping his business afloat and supporting his seven children, who live in three adjacent homes with a shared backyard in a Utah suburb. The fact that he and his wives are secret polygamists is the titillating hook of the show and the engine of its narrative, yet also the window into the drama's examination of far more universal experiences.

After laying out the architecture of the characters' relationships in the first season — particularly the enmity between Bill and Roman Grant, Nicki's father and the dictatorial leader of a fundamentalist polygamous sect — "Big Love" delves deeper this summer into the nature of polygamy and, by extension, the concepts of marriage, family and faith.

To Paxton, the series reflects a widespread preoccupation with the influence of modern life on the family structure.

"Americans don't have family like we used to," he said. "There's a subconscious longing in our psyche as a people for that extended family that is there to catch you if you fall and to support you in your triumphs.

"I think Mark and Will have found a really clever lens to refract all kinds of ideas and contemporary mores about marriage and family," Paxton added. "I think we could become, oddly enough, kind of the first family of television."

"Big Love" manages to be simultaneously empathetic and skeptical in its portrayal of polygamy. That duality is reflected this season in Bill's two eldest children, Sarah and Ben, who each wrestle with their feelings about their parents' marriage, with differing results.

At the same time, the show's writers sought to add more moral complexity to the character of Bill, who some critics complained was too opaque. The new episodes explore his vengeful side as he schemes to buy a video poker company that Roman wants.

"He's now not such a Job character with everything being heaped upon him," Paxton said. "He goes on the offensive."