The person that needs rescuing this time is Asha, so like usual, head to The Broken Shillelagh and head inside the simulation. After the cutscene introduces you to the mission, it's time to continue on. Asha's simulation plays like a certain tactical espionage game, so go to the first door and hold position until Asha opens it.
In this corridor, you will need to shoot out the lights and then continue past the guard, making sure to stay out of any remaining light (just stick to the outer edge of the room). When you make it to the next guard, Asha says you need to shoot out the light (which becomes a recurring theme in this mission), then you can sneak up on the guard and use stealth to kill him.
To get the next guard, you need to open the air duct, crawl through it and when you get to the opening on the other side, shoot out the light. Once you do that, drop down and yet again use stealth to kill the guard (you can shoot him in the head as well). The next spot has two lights and two guards, so do the same thing as before to get past them.
After Asha opens the next door, you'll be in an area with more guards. However, there aren't any lights for you to shoot this time, but as you approach the waypoint, both you and Asha will use cardboard boxes for cover. The first guard is stationary, but the other ones will be moving back and forth. What you need to do is sneak up behind them and perform a stealth kill.
Keep going through the hallways once you are finished with the previous section, until you come to a room full of lasers. Asha suggests going through them, but your character decides to just use the conveniently placed air duct next to them. Go through it and after the cutscene, keep going through the rooms, killing the henchmen in what becomes a firefight now.
Once you make it to the big room, keep killing the henchmen that appear until the boss fight with the evil you begins. The evil version of you has a sniper rifle and sticks to the second level up above. All throughout, more henchmen will appear, so it's definitely a wise idea to grab one as a hostage to help protect from shots from the evil you.
When you get the health of evil you down a bit, they will activate the generators nearby and use them to restore their health. As soon as you see them light up, shoot one of them until they deactivate. Keep doing this until you finally deplete all of the evil you's health, which will bring an end to the mission.