Clark Kent is the literal superman of the household, but his recently widowed mother is proving herself pretty super, too.

The actress who plays her on "Smallville," seen Thursdays on The WB Network and also in weeknight repeats on ABC Family, is embracing that development. Annette O'Toole feared Martha Kent would remain in the adventure's background, but that changed when Martha's husband, Jonathan (John Schneider), died shortly after his election to a Kansas senatorial seat. She has stepped up to fill his term, with ever-scheming Lionel Luthor (John Glover) taking a bit too much interest for her comfort.

Not that he isn't sharing her pain. "I was recently in a water tank all day," O'Toole reports. "Martha and Lionel were being tortured, and I felt like I was in a terrarium.

They built this 12-foot-high tank, and I was standing in various levels of water until it finally went over my head. Lionel was playing some kind of game with the tormentor, so it was sort of a combination of 'Saw' and something like 'The Matrix.' It's fun having done it, but while you're doing it, not so much."

Nevertheless, it indicates how central Martha is to "Smallville" again. "Boy, are they writing for me," the friendly O'Toole enthuses. "I get to work so much with John Glover. I've never seen anybody work so hard; he is such an amazingly dedicated actor, an inspiration, and just so much fun.

"I do feel bad about John Schneider, but it did free up this character in [the producers' and writers'] minds. I always felt there was potential they didn't tap into, but now they see her as her own person, not just an extension of Jonathan's fatherly ways."

Most mothers are proud of their children, and O'Toole feels that way as her television "son," Tom Welling, turns first-time director with "Fragile," the new "Smallville" episode airing Thursday, April 13. The Kents take in a youngster (guest star Emily Herst) after her mother's murder, only to learn the girl has unusual powers that enable her to shatter glass, making her a suspect in the death.

"He did such a great job," O'Toole says of Welling's turn at the helm. "We were all like proud parents, just standing around beaming. He had to work a lot with this young girl, and he was so good with her. It was really fun to see, plus it was like cutting out the director as middleman. Tom would ask, 'How did that feel to everybody?' We'd say, 'Great!' then he'd say, 'OK. We're moving on.' "

The acting relationship between O'Toole and Welling is also shifting, as Martha takes a bigger role in raising Clark into manhood -- or Superman-hood, as it were.

"There's much more of her being a confidante and friend to him," O'Toole says, "and also a moral guide, but he doesn't need that all that much anymore. He doesn't need someone telling him how to feel or what to do, and that's not just Clark Kent's story. That's every child's journey."

Very likely to be renewed for another season at this writing, "Smallville" will have a new home, since The WB will merge with UPN this fall to form The CW. "I wish they'd let us know for sure," O'Toole says, "but I can't imagine they would not rally around 'Smallville.' I really feel like we're just beginning to tell the story we want to tell."