What is the Song PDA by Interpol about? *its on rockband2*?

SUP! My sis' fave song on rock band 2 is PDA BY INTERPOL and i like it too. it has a sentece in it and i do NOT no what it means: Sleep Tight, Grim Rite, We have to hundred couches where you Sleep Tight.... And i DO NOT know what this song is about PLEASE HELP???!!!