In this still from "House of Cards," Washington actress Holly Twyford plays a woman who discovers her husband's affair. In this still from “House of Cards,” Washington actress Holly Twyford plays a woman who confronts her husband’s mistress.

Actress Holly Twyford has appeared in dozens of plays in Washington, logging hundreds of performances and earning Helen Hayes awards by the fistful. Our colleague, the theater critic Peter Marks called her “hands down the go-to stage actress in the nation’s capital.”

But it took just one line in a small part on the first episode of the second season of the cult-favorite Netflix show “House of Cards” to get the emails flowing.

“I’ve had friends from all over contact me to say they saw it,” says the actress, who’s currently performing in the Woolly Mammoth theater’s  “We Are Proud to Present.”  Despite her long and distinguished stage career, she says it’s the TV roles that make people take notice. “Even my family is guilty of it — when I was on ‘Homicide,’ they all said, ‘Oh, look, Holly’s on TV!’ and I was like, ‘Well, Holly’s been in plenty of plays, too.'”

To be fair, the House of Cards scene she’s in (and that line!) are pretty dramatic stuff, even on a TV series filled with quotable sound bites. Twyford plays the wife of a man who cheated on her and gotten his mistress — who happened to be on the “enemy” list of manipulative Second Lady Claire Underwood — pregnant. Tipped off by Claire, Twyford’s character ambushes the woman carrying her husband’s child.

“Use a condom the next time you [sleep with] somebody’s husband,” she spits.

Twyford says her own seven year old daughter won’t see the scene anytime soon. “Helena will be watching that when she’s 17.”

It was shot last summer on a Baltimore street, and Twyford wasn’t given the rest of the script when it was filmed, so she didn’t learn any of Season Two’s spoilers. And even if she had, they would have been wasted on her: Although she calls the show “incredibly well-done,” she’s not among its obsessed followers and didn’t know until recently how popular it was. Judging by the state of her in-box, “I now realize how many fans there are.”