Attendees of a Monday book party for Greta Van Susteren. (Bruce V. Boyajian)

It might have been one of the biggest moments in Washington dishing since . . . well, who knows? Some of the city’s most interesting characters had gathered together on a small stage at the Jefferson Hotel on Monday night to shoot a quick video in which they were about to confess their darkest secrets. Consider us riveted — and our recording device on to capture the moment.

Taking a break from mingling at a book party for longtime TV host Greta Van Susteren, the group — which included Sen. Amy Klobuchar (D-Minn.), White House adviser Kellyanne Conway, top lobbyist Heather Podesta, media consultant Tammy Haddad, former White House staffer Anita McBride and Joe McCain, the brother of Sen. John McCain (R-Ariz.) — were planning to test out Van Susteren’s new app, called “Sorry,” which allows users to send apologies that people can accept or reject.

On the count of three, the group chanted, en masse: “I’m sorry!” But wait, for what? Drat, they were leaving the juicy parts out this time.

Van Susteren, who is promoting the app in addition to her new book, “Everything You Need to Know About Social Media Without Having to Ask a Kid,” says she imagines the app will be used for both serious and lighthearted pleas for forgiveness. “This should be fun — it’s not a lot of hand-wringing,” she said. “I put my pets on there apologizing for shredding our mail.”

So wait, why an app? Van Susteren, who last year abruptly quit her longtime hosting gig on Fox News and went on to a short-lived show on MSNBC, says it seemed like the thing to do in the age of social media — besides, she had some free time. “When you’re unemployed, you look for something to do,” she said. “So I created an app.”

Well, some people take up pottery-making or hot yoga. But “some people” aren’t Van Susteren, whose eclectic roster of VIPs who turned out to celebrate the fruits of her unemployment included CNN’s Wolf Blitzer; literary agent Bob Barnett; Navajo Nation president Russell Begaye (you might have recognized him from the disastrous photo op at the White House earlier in the day when President Trump brought up “Pocahontas”); former White House spokesman Sean Spicer and his wife, Rebecca Miller, of the National Beer Wholesalers Association; GOP lawyer Ben Ginsberg; director of the National Institutes of Allergy and Infectious Diseases Anthony Fauci; Democratic strategist Hilary Rosen; and Roberta McCain, the 105-year-old mother of Joe and John.

Greta Van Susteren, left, chats with Kellyanne Conway. (Bruce V. Boyajian)

Conway was among those singing Van Susteren’s praises. “She’s one of the few women on TV who covers her shoulders,” she said. “I like that.” But when we asked what advice from Van Susteren’s book, which suggests some level of discretion (and proper spelling!) on social media, she might pass on to her famously Twitter-happy boss, she had less to say: “No comment.”

And though we’d been cheated out of a mass confessional, there was one secret in the room we just had to know — how does Roberta McCain stay so youthful? The matriarch, who sat in a wheelchair but greeted a string of well-wishers with bright conversation, said she wouldn’t miss a chance to support Van Susteren, who she called one of her best friends. “I just slap some makeup on and that’s it,” she said.