P.F. Sloan and Steve Barri, who at the time were just starting the band The Grass Roots, wrote this song. Secret Agent was a US adaptation of a hit show in England called Dangerman, and CBS needed a 15-second theme to replace the British version. Sloan wrote the guitar lick and the first few lines of the song, with Barri contributing to the chorus. This fragment, originally called "High Wire", was recorded as a demo by Sloan and Barri, submitted to CBS, and, to Sloan's surprise, picked as the show theme, which led to Sloan and Barri writing a [full-length version](https://www.youtube.com/watch?v=iC4O1ncLjMw) of the song. The original demo of the song used the "Danger Man" title, as shown by the surviving demo of the song, which Sloan sang. When the show's title was changed, the lyrics were also changed. Ultimately, "High Wire" was also retained by CBS, as it played over the episode credits following the "Secret Agent" titles. In 1965, surf rock band The Challengers [recorded a version](https://www.youtube.com/watch?v=PTOYLGkpcW8) for their album The Man From U.N.C.L.E. that features vocal harmonies, horns, and vibraphone. This would be the first commercial release of the song, though it was never released as a single and consequently didn't garner much attention.