Here's the chord progression (with - as always - the disclaimer that I might have something wrong):
Introduction
C minor | G major
Verses
G major | B minor | C minor | D major
G major | B minor | C minor | G major
Bridge
|: C major | G major :| E minor
A minor | B major | E minor
A minor | D major
The song is in G major, so that C minor chord (with its Eb accidental) is an outlier. Most of the titular line (all but the last syllable of "again") is sung above this C minor, so there's a musical tension attached to this sentiment. Furthermore, one of the vocal melodies sings "I don't want to see" to an A note. Combined with the Eb in the C minor chord, this forms a tritone, a dissonant feature that adds to the musical strain.
This odd C minor is also the chord beneath the phrase "Something wrong." The foreign tonality demonstrates the "something wrong." The second half of this line is "could be right," and the chord progression moves to a D major. Since D major is the dominant chord in G major, the "right"ness of tonality is restored.
The beginning of the bridge alternates between C major and G major chords, but at "day" in "You hid the light of day," the progression moves to E minor. The sadness associated with minor chords connects to the loss of "the light of day" mentioned in the lyrics.
