"Watcher of the Skies" takes its title from a line of the 1817 sonnet "On First Looking into Chapman's Homer" by John Keats. The song begins with a solo played on a Mellotron that the band had bought from King Crimson. Banks was "searching for chords that actually sounded good ... because of its tuning problems" and settled on the opening two chords "that sounded great ... There was an atmosphere about them". Banks and Rutherford wrote the music during band rehearsals at a gig at the Palasaport, Reggio Emilia in April 1972 during their first Italian tour. The lyrics were written in Naples a week later. They wondered what an empty Earth would look like if surveyed by an alien visitor. Banks described them as "a sort of sci-fi fantasy" loosely based on the novel "Childhood's End" (1953) by Arthur C. Clarke and the Watcher race of extraterrestrials featured in the Marvel Comics. Rutherford thought they were "interesting words but they didn't sing very well". Collins felt the need to bring in "some tricky arrangements" into the song's rhythm from seeing Yes perform live.