Bleake Island: Riddler Victims
Head northeast from Perdition Bridge into Chinatown, and grapple to the next overpass directly after the "Welcome to Chinatown" sign. Step on the switch here to activate a Riddler video. When it's over, use the Remote Batarang to scan the rioters and find the bomb victim. Throw another Batarang through the nearby electrical field to charge up, then nail him to deactivate the bomb.
This one is at the northeast edge of Chinatown, near the hotel. Step on the switch, use your Batarang to find the victim, and use another Batarang to pass through the current near the hotel sign to take him out.
The last victim is found just east of the Clock Tower, and the Riddler switch is on a rooftop overlooking the parade float nearby. Use the Remote Batarang to find the victim, then guide a second one through the electricity on the Urbarail track above and knock him out.