By RHONDA SCHWARTZ and MICHELE McPHEE

There is something wrong with the image that accompanies this story. Of the two $20 bills shown, one of them is fake. Can you tell which?

For its latest investigation, ABC News' "20/20? caught up with a master counterfeiter who says he taught himself how to make fake U.S. currency and printed $20 bills that were virtually undetectable - millions of dollars-worth.

"I'm the world's best counterfeit right now. No one better than me. It's me," Frank Bourassa says in the interview. "I started from scratch…"

WATCH the full ABC News Brian Ross Investigates report Friday night on "20/20? to see how Bourassa did it, how he got caught and why he's still smiling.

So, did you guess which bill is counterfeit?

[SPOILERS BELOW]

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The top one is legal tender, the bottom is its illegal twin brother. Tune in to "20/20? to learn how to tell the difference.