In an interview last night with Stephen Colbert, Glenn Greenwald of the Intercept said that he’s working on a story that will have the “biggest impact” of his various pieces on the modern U.S. surveillance state. “I genuinely believe that the story that’s the biggest one, that will make the biggest impact and will shape how the events of the last 10 months will be viewed by history is the story on which we’re currently working that hopefully will be ready in four to eight weeks,” Greenwald told Colbert.

And just what would that be?

The targets of spying by the National Security Agency (NSA) in America, said Greenwald. “Who are they targeting, for what purposes? Who are these people that they are declaring to be sufficient threats that it warrants reading their e-mails? And what is the pattern of people that they’ve targeted? Are these political dissidents, are they critics of U.S. foreign policy, are they actual terrorists? And that’s the reporting that needs to be done?”

When Colbert asked whether it’s “good news,” Greenwald replied that there are “some really interesting revelations in there.”

Greenwald’s work on the NSA based on leaks from Edward Snowden anchored a series of stories in the Guardian that last month won the Pulitzer’s public-service award (along with The Washington Post). His new book, “No Place to Hide,” chronicles the negotiations with Snowden and provides “fresh information on the NSA’s unprecedented abuse of power with never-before-seen documents entrusted to him by Snowden himself,” according to the book’s promotional materials.

Often a feisty and combative presence in his media interviews, Greenwald smiled his way through a compelling discussion with Colbert, who pretended to be outraged by the Greenwald-Snowden collaboration. The comedy backdrop even induced him to go soft when Colbert asked about a hot-button topic: “Ed Snowden has revealed national security secrets, has now fled the country, he is a traitor to the United States. Why should you not be prosecuted for aiding and abetting an enemy of the United States?”

Greenwald replied, “Yeah, I mean, that’s the argument that has been made every single time somebody comes forward in an act of conscience — like Daniel Ellsberg did in 1971, and revealed that the American government was systematically lying to the population about the Vietnam War. And everyone said, or a lot of people said, ‘He’s a traitor, he’s damaging national security.’ ”

When asked that same question last year by NBC News’s David Gregory, Greenwald responded a bit differently.