If he has not slipped your grasp, the final encounter will be on Bleake Island at the Cauldron Fire Station (Coordinates 2108, 2456) near the GCPD, where you must chase him down one final time.

After which, drive to the Otisburg Fire Station (Coordinates: 2630, 1469) and repeat the process for taking him out. The second encounter won't be available until you have Batmobile access to Founders' Island as part of the Main Story. Note that if he manages to get away from you, he will go to another fire station, even if it's one you've already chased him away from. When his fuel is depleted, get close to him and preform an aerial attack (tap the attack button once and then press and hold) to fly out and stop him. You won't be able to attack him until his fuel meter has completely depleted (although he'll occasionally get a small amount back after at time). Now you'll have to chase him as he flies through the streets of Gotham, avoiding the large pools of flame he'll shoot onto the streets, and remain enough to him at all times. To deal with the blaze, use the Power Winch on the base of the Fire Station to trigger the sprinklers, and catch the arson red-handed: Firefly. You can find the first fire on Miagani Island at the Bristol Fire Station (Coordinates: 3388, 2289).

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