First off, a quick summary and a reminder at the same time. The quarantine wall that you need to get across, is located in the [Rudshore Gate], and the neighboring square is being patrolled by both regular guards and tallboys. An important piece of information is that the next area cannot be reached in a standard manner, because you are separated from your destination by an active wall of light. Below, there are suggested paths to follow here.
Variant 1; approach the quarantine wall from the left) If you want to approach the quarantine wall of light from the left, you need to get through the ruined buildings, mentioned in one of the previous subsections to this guide. It isn't too demanding a process, but it is a good idea to make sure you don't remain near windows, and other exposed spots, for too long.
After you sufficiently near the wall of light, you should notice a power supply whale oil tank. Since you cannot reach the tank, and remove it, the best idea is to destroy it using your crossbow. After the wall of light is disabled, you can resume on your path, being, at the same time, mindful of tallboys.
Variant 2; approach the quarantine wall from the right) If you want to approach the quarantine wall from the right, you need to walk near the building in which the survivors stayed. It is better to stay on the lower floor (the above screenshot), because this minimizes the risk of being spotted.
After you get sufficiently close to the wall of light, you need to use Blink (teleportation) to teleport to the balcony that is adjacent to the wall. Meanwhile, you should also avoid being spotted by tallboys. After you reach the upper balcony, use Blink again to avoid the live wire and approach the tank to remove it, and to disable the wall.
Variant 3; take the rail) The most interesting one of the available variants. It allows you to go around all of the tallboys around the wall of light. If you are going to take the rail cruising around the area, start where bodies are dumped from the bridge (the above screenshot).
The plan assumes that you get to the roof of one of the buildings, so that you can jump off of it onto the rail's roof. You need, therefore, start climbing up the buildings to your left (the above screenshot).
While climbing, you of course need to aid yourself with Blink (teleportation), and try not to lose your balance. Your destination here, is the roof shown in the above screenshot.
Position yourself directly above the tracks and wait for the rail to come, which may take a little while. When the rail stops and starts dumping bodies, use teleportation once again to mount it.
The rail should soon pull away. You cannot yet relax, because, as you can remember, you are nearing an active wall of light. You, therefore, need to jump off the rail sufficiently early, or use your crossbow to shoot the power supply tank on the move.
New Main Quest: Travel to the Old Port District
Summary) All of the variants described above, will allow you to disable the wall of light and, at the same time, get to the other side. Jump down to a lower level and find the door shown in the above screenshot, thus reaching the [Old Port District Outskirts]. Approach the second door and wait to be taken to a new location.