Eugene Chaffee is one of the primary antagonists (alongside Stewart Rogers) of This Is The Police. He is a Freeburg restaurateur and businessman, who is opposed to the policies and personality of Mayor Roberts.
Chaffee is the true identity of the anti-Mayor Roberts campaigner Robespierre, revealing his identity to Jack after his first convalescence. Chaffee's goal is to overthrow Mayor Roberts, and create a progressive Freeburg under his leadership. It is also discovered that he is entirely responsible for the creation of the Dentist in Freeburg, masterminding the ruse for his and Jack's benefit.
In the third act of the story, you will have the choice to side with either Rogers or Chaffee. If Chaffee is chosen, you will have to storm City Hall to take down Rogers. Jack will still be fired from his position, but Chaffee will reward him with "enough money to last Jack the rest of his life" - one dollar.