How to unlock: Meet with Alfie in the Tower lobby (Tower on the map).
Difficulty level: medium
Reward: 4500 experience, blueprint (Electricutter)
You can start this mission after completing the Airdrop main quest. Reach the lobby on the ground floor of the Tower and find Alfie. Talk to him and he will ask you to reset two substations. What's important, is that you can prepare the traps connected to the quest only at night. If you talk to Alfie during the day, you have to wait until the night comes. You can use the bed on the nineteenth floor in the Tower or one of the beds in the substations marked on your map. It is a better idea, because you won't need to travel to the place at night.
You have to reach two substations - the one in the north (number 4a on the map) and the one in the east (number 4b on the map). When travelling, stay out of the sight of the infected (use Survivor Sense to locate them). It is a good idea to us a Night Vision Booster to see better and avoid the enemies. The only way to enter the small building in the northern substation is to break in using a lockpick, but the lock is not easy to break. Interact with the levers in both the substations and bring back the energy supply.
Your next objective is to reach the central station located in the southern part of the Slums (number 4c on the map). Just like before, avoid being seen by the infected and by the "elite" zombies. The central station is occupied by a lot of usual infected and it is better to not get into any fights. Rely on climbing and try to go above the monsters. You have to locate the main terminal, which can be found in the building in the south, marked on the map in this guide. Interact with the terminal and you will unlock a new safe zone and complete the quest. Don't forget to go back to Alfie to collect a Blueprint (Electricutter).