Fergus' Arm location
If you chose to save Fergus Reid, you will have to find his arm after a party during the story. To find Fergus' Arm, walk around Eva's Hammer and talk to people until you can narrow the arm's location down to the hangar. Walk up to the top floor and look for two boxes that block the way to a vent. Use your energy weapon to shoot holes into the boxes, then follow the vent until you find Fergus' Arm. Return to Fergus Reid and give him back his arm to complete the quest.