Green uses the poetry of Walt Whitman to be the voice of Margo’s inter self or inter voice.  When Margo leaves Quentin finds her copy of Leaves of Grass by Walt Whitman and there are several passages that have been highlighted.  Q decides that if he can understand the highlighted parts he will find Margo.  Margo has highlighted Unscrew the locks from the doors!  Unscrew the doors themselves from their jambs!   After thinking about it, Q goes to Margo’s house and takes her door to her room off and looks for a clue.  He finds nothing.. He finally looks on the door to his own bedroom and finds a piece of paper with an address.  He knows Margo has left it for him and believes he will find Margo at the address.   So he plans to go there during school the next day.  By following these passages Q finds Margo and moves the plot along.