The first mention of "HR".
A song is played in the background of a scene between John and Fusco. It's called "If I Had A Heart" by a Swedish recording artist, Fever Ray. It is now played during the opening credits of the History Channel's Vikings (2013).
It is established that John Reese is originally from Puyallup, Washington, which is 95 miles away from Mount Vernon, Washington, the real life birthplace of Jim Caviezel, who portrays Reese.
The title of the episode refers to the "Blue Code of Silence", sometimes known as the "Thin Blue Line", an unwritten law among police officers not to report on another colleague's errors, misconducts or crimes.