Barney and Harris butt heads when Harris refuses wear his uniform in the Police Department's annual day in uniform day. Wojo and Harris bring in a letter carrier who got caught not delivering mail he deems unimportant. Dietrich sets out to solve a seven year old cold case.

Following Dietrich's arrest at the anti-nuclear rally, Barney tasks Harris to book him while the others go downstairs to assist the officers in dispersing the riot. His arrest also results in a visit from Internal Affairs. Another protester, who happens to be a nuclear engineer, is booked for splashing his fellow protesters with atomic water.