Fan Casting “The Rat” in Gotham (Season Three)

Gordon and Sarah learn from Sal Maroni that someone who’s working for the GCPD has been in cahoots with the Falcone Crime Family for a while, and has been sending them information. By the end of the season, Gordon learns that The Rat was in fact his partner, Arnold Flass. But before he can tell the police department, Flass frames Gordon, claiming he’s The Rat, and has him arrested.