Plot hole: It turns out in the climax of the episode that there are no bullets left in the gun and Miss Fisher knew it. That would mean then that she deliberately wasted minutes with Simon bleeding out on the floor when Chaim was holding them at gunpoint with an empty revolver, for no discernible purpose.
Plot hole: Guards at a security checkpoint attack Varrick and Bolin, because a wanted poster identifies them as fugitive traitors. The problem is that poster cannot have been there. Varrick and Bolin escape in the previous episode (Battle of Zaofu) but are captured minutes afterwards. (So, no posters needed.) The next day, they escape again by blowing up their imprisoning train car. Their captor, Bataar, thinks they are dead. Indeed, Varrick intended to die. Later, Bataar is actually shown reporting them dead. One might argue that the poster wasn't a wanted poster, but one that warned people about the empire making an example of the traitors.This argument is too flawed: The empire had many examples already, some very high-profile. And a propaganda poster must be placed in plain sight, not in a security booth corner especially designated to let security guards compare the passing individuals. (00:14:00)
Plot hole: Will is telling Mac that the DOJ is being out-lawyered by a group of financial institutions, including Lehman and Countrywide, both of whom went out of business in 2008, well before the date of this episode on New Year's Eve 2011.
Episode #4.1 - S4-E1
Plot hole: When DCI Roz Huntley kills Forensic Coordinator Tim Ifield the crucial piece of damning evidence is her DNA under his fingernails after scratching her arm. Problem being, at the time of his murder, he was wearing surgical gloves. (00:56:40)