Lyric discussion by jasonsaucier 

Cover art for 20 Years lyrics by Civil Wars, The

I think this song is about giving up a child.
They wrote a note when they gave up the child for adoption but it was never delivered. 20 years later they finally deliver the note with a "faded picture" and a "shadow you won't recognize". A letter with a "secret" (possibly gave up the child to someone in the family, they have "no excuses, no alibis". They now pray for redemption and pray that they will receive a note under their door and will wait 20 more years if needed.

Song Meaning