Luke Waters was born in Ireland and had dreams of following in his grandfather's and brother's footsteps by joining that country's police force.  Waters did fulfill his dream of becoming a cop -- only in New York City.  He spent two decades with the NYPD.  Waters details his experiences in a new memoir called NYPD Green: An Irish-Born Detective's Twenty Years on the Mean Streets of New York.  He joins us on this week's Cityscape to share his story.