Showing a vulnerability that is out of character

That face, composed in its porcelain smile, is a shield with which Bree Van De Kamp meets the world.

As any viewer of “Desperate Housewives” knows, Bree has plenty not to smile about. Last season her husband died -- and worse (as she discovered later), it was at the hand of George, her twisted admirer. Then this murderous swain offed himself in an ill-advised gamble that Bree would demonstrate her love by saving him from his drug overdose.

Meanwhile, Bree’s teenage son is scandalizing her by coming out of the closet. And she seems to have developed a drinking problem.

Even with Bree’s defensive smile, it’s mighty hard to keep up appearances on Wisteria Lane.

But here is Marcia Cross on break from playing Bree, and she presents quite a different picture.

Oh, the red hair and porcelain skin are the same. But in person, Cross comes across as far more delicate and vulnerable than Bree would permit for herself on the hit ABC series.

Indeed, Cross is focusing on a lifelong vulnerability. As a paid spokeswoman for GlaxoSmithKline, maker of a migraine headache medication, she wants to talk about her long affliction with migraines and what she’s done to combat it.

“I suffer from a classic migraine,” says Cross, 43, whose headaches began when she was 14. “My fingers tingle, and I see a very odd sort of aura in my peripheral vision. I know when it’s coming on, and I take my medication, and in a number of hours I’m back on my feet again.

“But before that, I was knocked out and writhing in pain, and it was horribly excruciating.”

More than 28 million Americans who suffer from migraines, three times more women than men are affected -- and tightly wound, control-freak Bree would seem to be a ready candidate.

Cross laughs at the thought of her own ailment imposed upon Bree. But then it dawns on her: The idea might just work.

“I might have to ask Marc about putting it in,” she muses.

She is referring, of course, to “Desperate Housewives” mastermind Marc Cherry, who created Bree and the dishy dames played by Cross’ costars Teri Hatcher, Felicity Huffman, Eva Longoria and Nicollette Sheridan.

“I’m still pinching myself, I really am, at my good fortune” at being signed for the show, says Cross, for whom lightning has struck twice: In the 1990s, she starred on another wildly popular series, the Fox soap “Melrose Place.”

“I never thought I would live Kimberly Shaw down,” says Cross with a laugh. Each show ranks as a cultural phenomenon, but Cross points out that, unlike “Desperate Housewives,” “Melrose” was never exactly a critical favorite.

“It’s very nice to be able to do your work and be respected for it,” she says. “It’s not that my work is any different, because I always took ‘Melrose’ very, very seriously. I would pretend it was some really important film, every day. But I don’t have to make any excuses for this one.”