NEW YORK -- Last season, "Billions" performed a delicate balancing act.

Chuck Rhoades, the powerful and perverse U.S. Attorney (played by Paul Giamatti), was locked in a legal cage match with hedge-fund titan Bobby "Axe" Axelrod (Damian Lewis). But through it all, Wendy Rhoades kept a foot planted in both worlds: as the wife of Chuck and top aide to Axe.

Now, in this Showtime drama's sophomore season, the equilibrium is shattered. Wendy has separated from her husband and bolted from Axe's firm, leaving those combatants to clash even more ferociously.

The only sure thing about the narrative shakeup: Wendy Rhoades can take care of herself, and, when necessary, cut Chuck and Axe down to size. On a show that pits two Alpha Males against each other, Wendy stands tall as a reigning Alpha Woman.

"This season you see her trying to walk a line with each of them while she maintains her dignity and distance," says Maggie Siff, who brings Wendy vibrantly to life. "To find her own moral centre, she had to shed the two of them."

On the premiere (Sunday at 10 p.m. ET), you'll see Wendy spurn Bobby Axelrod's overtures to return as the in-house psychotherapist and performance coach.

"There's this thing that happens when we're in a room together," she says sharply as he works his charm. "But I'm shutting it off. I HAVE shut it off."

And you'll see her stand up to Chuck when he rages, "I always knew I'd end up smeared by Axelrod's poison," for which he blames his wife as having served as the carrier: "Proximity is enough."

"I no longer have proximity to it," she sneers, "and YOU no longer have proximity to ME."

Wendy is an unusual character for series TV, and a distinctly different character than Siff has played in the past. And yet all her women share a common bond: They're strong, smart and commanding even in a crowd dominated by men.

For six seasons on FX's hit drama "Sons of Anarchy," Siff played Tara Knowles, the physician wife of a motorcycle-gang leader who could hold her own, and then some, in that wild-and-woolly world. (At least, until she was stabbed to death in her kitchen with a barbecue fork by, ironically, another woman: her mother-in-law and the club's grande dame.)

"When we first started that series (in 2008) I didn't expect it would become the sensation it did," says Siff in her quiet, thoughtful way, "but it tapped into something tribal in the audience's psyche. It was so pulpy in its violence, yet also had this operatic family drama at its centre even when the violence crossed the line -- MY line, at least. There were scenes I couldn't watch!"

Siff came to "Sons" from her brief but emblematic stint early in "Mad Men," where she played Rachel Menken, the bold heiress and boss of a New York department store who became romantically involved with ad man Don Draper.

Unlike so many of his conquests, Rachel soon recognized that their relationship was not one for the ages. She cut her ties with Don, this caddish married man and dad, when he proposed they leave it all behind and run away together.

Years later, Don (and the audience) would learn that Rachel had died of leukemia -- but not before she made a brief comeback.

Siff was pleased to shoot this fleeting encore for the series' final season.

"I always wanted Rachel to circle back through that world," she says.

But the one-minute scene she was asked to play (the only portion of the script she was privy to) made no sense to her, especially after series star Jon Hamm tipped her off that her character was dead.

"I said to (series creator) Matt (Weiner), 'What's going on?' He said, 'It's a dream. Just do a dream!"'

She did, with a chinchilla coat obscuring tell-tale evidence that she was pregnant with Lucy, now 2 1/2, by her husband, design consultant Paul Ratliff.

"I had no idea how the scene lived inside the episode until I saw it on TV along with everybody else," she says.

A woman who began her career in experimental theatre in Philadelphia and then off-Broadway, the Bronx, New York native, now 42, admits to surprise at her repeated success in TV drama.

But surprise has been a driving force in her career, she explains: "You have to surrender yourself to what finds you in this life."

Despite no sign of surrendering, she finds herself now in an acclaimed drama alongside two leading men she calls "phenomenal actors and phenomenal human beings.

"Damian is so subtle but so precise as an actor," she says, "while Paul charges out of the gate with so much life. Their energies are very different. It's fun to float between them as scene partners."

And for "Billions" viewers, there's more fun ahead watching Siff power between them as the forceful link in this tangled tale.