Search for the Slider Projector in Dimensional Research
Leave Darling's Lab and go to the left. Use the button to open the huge doors, which will put you back by the turntable. More Hiss will spawn, so take them out then go through the south exit to reach the Control Point. Fast travel to Central Research then head to the entrance for Dimensional Research, which will be surrounded by Hiss.
Find Ahti the Janitor
Cross the walkway and go into the Ashtray Maze, then claim the Control Point by the entrance. You can't actually complete this yet though; you need to use the Control Point to fast travel to the NSC Power Plant, then go to the Janitor's Office through Ventilation.
Follow Ahti's visions
Interact with the painting in Ahti's office, then start following Ahti's visions, first through the pipes with a few Hiss enemies, then down the walkways. You'll reach the NSC Coolant Pumps Control Point; claim it, then go down the corridor and into a huge area covered in mould. Clear out all the enemies then cross to the other side, where you'll find another cord to enter the Oceanview Motel.
Ring the bell twice, then go into the middle room and turn on all the radios. Ring the bell again and turn on all the radios in that room, then ring it one more time to open up the final room and grab the key. Head back to the lobby and you can open the Janitor door, not the usual door at the opposite end.
Now you're in Black Rock Quarry. There's enemies in the middle you can fight if you wish, or you can sprint and dash round the side of the quarry to avoid fighting. When you reach the other side, drop down the elevator shaft to find the Restricted Area.
Run to the office and kill the Hiss Guard, then hit the red button to spawn a bunch more enemies. Once you've killed them all, hop on the yellow cable car-esque vehicle and travel into the mist. When you reach the other side, go down the stairs and run towards Ahti's vision.
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)
