Complete A Matter of Time to obtain this side mission.
Investigate the Safe Room
Fast travel back to the Sealed Threshold Entrance, then make your way into the same room you found the Japanese Paper Lantern during the Langston's Runaways quest. At the back of the room is the Shelter you need to investigate. Make your way inside and you're faced with a boss fight against The Anchor.
This is another boss that doesn't put up much of a fight. There's four platforms on each edge, and The Anchor will look at each of them in turn, spewing clocks out. You want to be on those platforms, because it's the only way you can use Launch to hit The Anchor where it's vulnerable. Bring up your shield to protect yourself from the incoming clocks and as long as you don't get swarmed by the few smaller enemies that spawn, you should be fine. Just keep using Launch and if you need to deal a small bit of damage to finish it off, your service weapon will work even when The Anchor isn't facing you.
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)
