As when you first visited the Warren, the first priority is getting a way open back to the previous island. Fortunately, part of the Historic District is already lit up and the bridge back to the Warren is in the lit part – no running through the dark yet.
This being your first visit to the third island, there's something you should know. Almost all the roofs are mined, some with more than one mine. So no flying over the rooftops; you'll have to approach each new roof with care looking for flashing red lights. These lights indicate a mine (or more than one) is on the roof and you'll have to locate it and shoot it or it will blow you up. The mines are small discs lying on the roof with the flashing red light on top.
Restore the bridge[edit]
Proceed to the marker on your map and lower the bridge. Try to avoid First Sons along the way – even though this part of the city is lit up, you don't want any major firefights along the way. Make sure you're fully recharged before zapping the bridge panel to lower it. You'll meet First Son Conduit #1. These guys turn themselves into giant, neon purple "ghosts" that look a lot worse than they really are. They only have a melee attack (granted, it does a lot of damage) and they're slow. Stay away from it and pepper it with Lightning Bolts until it resumes normal form and then blow that normal form up before he recovers.
You receive a message that people are being held hostage and you have one minute to rescue them. Don't dawdle heading for the marker on your map. There's no timer running on the screen, but you really only have one minute (give or take a few seconds).
The captives are, of course, surrounded by gangs, but you can't go in indiscriminately blasting away or you'll kill the hostages. Use Precision to get rid of the First Sons closest to the hostages (you'll recognize them by the large electrical fence surrounding them), then run in and drain the fence to free the hostages.
You will be attacked. Now you can proceed to indiscriminately blow stuff up. Use everything you've got to defeat all the First Sons in the area, probably including another giant Conduit. Now you get a message that a second set of hostages has been captured. These folks are along the southeast side of the park and approaching along the street is suicide because of a machine gun turret. On the other hand, you don't have time to go around the park.
The doctors and Trish[edit]
Proceed through the park and meet First Son Conduit #2. These guys are invisible until they shoot at you. Considering they materialize right next to you and fire some type of explosive weapon that drains more than half your health in one shot, your first encounter with these guys is many times your last. You have to know where they are and where they're going to come from, which you usually don't find out until you're dying.
There are two of them in the park and they hang around the playground. When you see a swing set, start throwing grenades. Your only hope of beating First Son Conduit #2 is to shock them into visibility and then hit them with Lightning Bolts. Fortunately, they can't take as much damage as they dish out. Getting hit with a Grenade followed by a couple of Bolts usually does them in.
Once you reach the fence along the southeast side of the park, run northeast along it past the turret (which faces southwest) and Precision hit the gunner and his partner. Drain the fence holding the hostages and take out the First Sons that gather to celebrate your heroism.
You'll have to travel back across the park to get to the third bomb, but there's not as much opposition as the one you just took out. Afterward, however, there's a big Karma moment (and probably the only real moral dilemma in the game). The Good action is to save the doctors. The lives of the many are worth more than the lives of the few, or the one in this case. The Evil action is to give in to your selfish desires and save Trish.
Make your decision – the doctors are on the round building to the southwest (your left) and Trish is further away on a building at the corner of the intersection to the northeast (your right). When you reach the roof, the mission ends with a cut scene resolution.