Pickle caught wind of an item in the factory and sent his friend there to grab it. However, Harry hasn’t come back yet and he’s been saying the place is haunted. To find the place, head to Titan Industrial Facility and go all the way to the big, open area past where you first met Gladstone. Here, you can find an area that leads underground, which is where the exit to Sub-Level 13 is located.

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You can’t hurt these ghosts yet, so ignore them and go into the vent to continue (right).

Straight ahead of where you enter is an elevator that goes down, so take it. Head straight from here and you’ll find a spot where you can drop down. Go into the side room down here and you’ll see a ghost, which you can’t hurt with your normal weapons. You’ll hear a voice telling you to shoot the junction box, so do that and then go into the vent. Of course, Harry will be there, dead and all, so have a listen to the ECHO and then interact with the body to finish the mission.