Finally, the artist with fans who never have to go into a museum to admire his work. In fact, they race to find it after clues on facebook and twitter. He's now e verevealed an october surprise. His works are far more famous than his face. In fact, few of us have ever seen his face before. One of his fans thought he caught a glimpse this past week, but no one knows for sure. Banksy, a legendary british street artist, whose works are now popping up all over new york city. All this month, new piece of work every day, somewhere in the city of more than 8 million. He's made his mark here before. Several of them. All over l.A. The year he was up for an oscar for his documentary, never revealing his true identity. He didn't even show up. Ultimately, he can't show his face. If he's a face, if he's a person, they can come arrest him for defacing property. Reporter: Banksy's work now commands a lot of money. On his website, he's revealed that this month, he's going to be an artist in residency in the streets of new york. But nobody knows where until it suddenly appears, location spreading faster than his paint. Across facebook and twitter. His fans even beyond the art world showing up with their iphones and their cameras. To be honest, it's a once in a lifetime opportunity. Because, the thing is, they're here and then they're gone. It's not like seeing a leonardo, a "mona lisa," where you can go see it. This is going to be gone in literally three hours. Reporter: Look at this mom pushing the stroller, her face when she realizes she's there too late. And then the dad just in time elsewhere, his little boy planted right there in front of the work. In fact, that door, a complete stranger offering the owner $1,000 for it. And a replacement door from home depot. His last piece sold for $400,000 and it was a piece of hang that up on my wall. Reporter: The owner? No thanks. Tonight, that work covered up for the owner himself.

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