David Bowie was "the man who sold the world," all right--the man who sold the world on the idea that he was retired for good.

It was only in January that we found out his decade-long disappearance wouldn't be a permanent one--when he used his 66th birthday as the occasion to spring a new single on us without so much as a leak that he'd even darkened the doorway of a recording studio. With this week's release of his comeback album, The Next Day, he's the man who got good reviews from the world, too, as critics rush to proclaim it his best work since the 1980s, if not '70s.

The supersecrecy leading up to the release represents quite a hat trick in an age when literally almost nothing about celebrities is held secret. How'd Bowie manage to pull the wool over our eyes for the past 10 years, when fans assumed he was in failing health since his 2004 heart problems, or content to quit the business to quietly raise his daughter out of the limelight, or both?

For starters, he wasn't fooling for the first eight of those last 10 years, when he apparently really had resigned himself to musical inactivity. "I’d had some correspondence with him where he’d said that he just wasn’t interested in writing music any more," his longtime bassist, Gail Ann Dorsey, told England's NME magazine, "because he didn’t have anything to say."

But the muse had struck by November 2011, when he contacted producer Tony Visconti to start the process. But Bowie didn't want anyone to know, and there's a short answer to how he managed to keep a lid on the recording process for over two years that can be summed up in four short letters: NDAs.

Bowie isn't doing any interviews to chat about the new album, much less tweeting about it, so some of his motives remain a mystery--even to the people who worked with him on it, since they apparently weren't much inclined to probe him for deep psychological details. But a handful of them have spoken up about how the process went down, and it borders on cloak-and-dagger stuff. The intelligence community may want to take some tips.

As drummer Zachary Alford has said: "It was like being in Mission: Impossible."

Guitarist Earl Slick has worked on 10 Bowie albums, including the classic Station To Station. He told Ultimate Classic Rock this one was a little different. "One day I went out to have a cigarette in front of the studio, and something felt weird...and I peered across the street, and there was a guy there with a camera on a tripod. So I put my cigarette out and went back inside, 'cause if they see me, they can put two and two together." There was an initial giddiness to the secrecy, Slick said, "but after I got all excited after I finished doing the tracks and I was bursting, it wasn’t fun anymore...Do you have any idea how many interviews I’ve done... with this under my belt, which I couldn’t say anything about? It was horrible...especially because I had the cover for the Christmas issue of Guitar Player magazine...and they did a 14-page spread on me, and I’m thinking, 'Christ, I can’t even say anything.' Anyway, he appreciated that--and I got a nice 'thank you' for keeping my big mouth shut."

There are reports everyone involved had to sign a non-disclosure agreement, although the musicians involved have only talked about oral commitments. As Visconti told Rolling Stone, "He said, 'Keep it a secret, and don't tell anybody. Not even your best friend.' I said, 'Can I tell my girlfriend?' He says, 'Yes, you can tell your girlfriend, but she can't tell anybody.' The real trick was just not telling even your best friend. Bowie fans are just unpredictable–if they hear news like this, the cover would have been blown years ago. Now one person did leak it, but nobody believed him... Robert Fripp! He was asked to play on it, he didn't want to do it and then he wrote on his blog that he was asked. And nobody kinda believed him."