To get Fridge Duty, speak to the bloke staring at the refrigerator during My Brother's Keeper.
Assist the Agent in the Panopticon cell - 4th Floor
Fast travel to the Upper Panopticon and use the intercom to speak to Phillip, the bloke inside the cell. Afterwards, fast travel to the Panopticon Entrance and go through the Security door to speak with Langston, then go back up to Phillip and go through the door. Interact with the fridge to try and cleanse it.
Former boss fight
Now you've got a boss fight in the Astral Plane against the Former. The trick here is to use Launch to grab the orbs it fires at you and send them back at it when the eye is open. As you deal more damage to it, the Former will start trying to stamp on you, so just be prepared to use Evade when it lunges. Aside from that, the boss fight is relatively easy, just dodge and throw. When you're done, go back and speak to Langston to complete the mission.
Main Missions:
Control walkthrough: Welcome to the Oldest House
Control walkthrough: Unknown Caller
Control walkthrough: Directorial Override
Control walkthrough: Old Boys' Club
Control walkthrough: Threshold
Control walkthrough: My Brother's Keeper
Control walkthrough: The Face of the Enemy
Control walkthrough: Finnish Tango
Control walkthrough: Polaris
Control walkthrough: Take Control
Side Missions:
Control walkthrough: Old Friends
Control walkthrough: Fridge Duty
Control walkthrough: Self-Reflection
Control walkthrough: Mr Tommasi
Control walkthrough: Old Growth
Control walkthrough: A Matter of Time
Control walkthrough: Langston's Runaways
Control walkthrough: The Enemy Within
Control walkthrough: Mold Removal
Control walkthrough: What a Mess (all missions)
