A Smithsonian event all about secrets turned into a very public proposal for one couple.

“Smithsonian at 8” held its latest after-hours event at the National Postal Museum on Friday night, this time featuring PostSecret, an ongoing community art project in which people write a secret on a postcard and send it anonymously to project creator Frank Warren, who lives in Germantown, Md.

Warren has collected more than a million postcards since he started the project in 2004, and they’re all collected in a giant pyramid at the National Postal Museum’s exhibit, “PostSecret: The Power of a Postcard,” which is open until September 2017.

Guests at the event were treated to a private viewing of the exhibit. But before the DJ and the cocktails came out, Warren was on hand to share some of his favorites.

And we’ll let you in on a secret: The last postcard he read was a plant.

Stephan Evans, a 29-year-old government contractor, was there to propose to his girlfriend, Ashley Ortiz.

Watch the video above to see how it happened.

Initially, Evans had contacted Smithsonian officials, wondering if they would place a proposal postcard in the exhibit, “and it just snowballed from there,” he said.

“There’s never been a better ending to a PostSecret event in 12 years,” Warren said.

If you want to send a secret to Frank Warren, you can mail it to:

13345 Copper Ridge Road
Germantown, Md. 20874