This was inspired by an acoustic song called "I'm Confused" that Jimmy Page heard folk singer Jake Holmes perform. When Page was a member of The Yardbirds, they played on the same bill with Holmes at the Village Theatre in New York City. Holmes' version was about an acid trip, but contained many of the same elements that made their way into the Led Zeppelin version: walking bass line, paranoid lyrics and an overall spooky sound. The Yardbirds played the song in concert, but never recorded it for an album, although they did play it for a BBC taping in March 1968.
Led Zeppelin's version was not credited to Jake Holmes, as Page felt that he changed enough of the melody and added enough new lyrics to escape a plagiarism lawsuit. While Holmes took no action at the time, he did later contact Page in regards to the matter. Holmes finally filed a lawsuit in 2010, alleging copyright infringement and naming the Led Zep guitarist as a co-defendant. It was the favorable judgment for organist Matthew Fisher in the "A Whiter Shade Of Pale
" case that convinced Holmes to sue, as precedent was set that songwriting credits could be challenged in British courts many years after the fact. Unfortunately for Holmes, his case was dismissed on January 17, 2012.