Part 4: Recursions

1. Recursions and Iterations

After the CFD, the Sinkhole is deeper and Patterned, and Pope asks for help. The mission goes down through the Sinkhole into the Underpass, looks for a research team that keeps appearing and vanishing, and ends by placing the last probe relay at the very bottom. Rewards: 1 Living Shard, Grist's Tracking Device and the Prime Candidate Restraint Suit.

• 1

  Pope in the lobby, then into the Sinkhole

  From Dylan's cell, follow the path to the lobby and talk to Pope; this also starts the side story Into the Valley of Death (Langston, at the Field Office). Enter the Sinkhole through the laundromat, the way you left it last time. Drop to the PERSONNEL ACCESS platform and follow the yellow tape and arrows down to the lowest level, into the hole in the middle, then down the ropes with white lights. Go down the hole where you used the diving bell before and take the stairs into the Underpass.

  • Power Upgrade crate #1. Inside the laundromat building as you go in.
  • Fast travel door: Sinkhole. At the bottom of the white-lit ropes.
  • Power Upgrade crate #2. Left of the south door, below the Sinkhole, before the stairs.
  • Optional: on the way down, a higher platform holds Dombrow, who belongs to Into the Valley of Death.
• 2

  Down the Underpass to The Spire

  Jump to the red platform below and go right along the white lights, clearing the Hiss. Before you climb the pillar, a drop to the left leads to a shop and a Health Point crate. Climb the pillar, cross and fight; afterwards jump up to flip onto the ceiling, drop into the hole, land on the Patterned platform and climb to its top. Follow the lights south and call out the red light in the distance to move the objective on.

  • Health Point crate. Down to the left before the pillar, by the shop.
  • Fast travel door: The Spire. At the end of the light path. The Spire is also where the Underpass Resonant starts, on the Resonants page.
• 3

  The beacon: Map Kit, Halfway Trail and the first use of Reach

  Go to the lower part of the platform and down the middle ropes. Follow the path right towards the beacon and clear the next platform, then take the left path. From here the route needs Reach: if you have not done The Subway Fault yet, fast travel out and do it now. Jump to the yellow-lit platform, cross to the red floor, follow it past a Hiss to the beacon walkway, and inspect the group of bodies for Zoe.

  • Map Kit. On the left at the bottom of the ropes.
  • Fast travel door: Halfway Trail. Along the left path, before the yellow-lit jump.
• 4

  The search area, Grist and her device

  A large search area opens. Inspect the Cable Car in the east corner; you will use it later. West of it, climb the pillar for the next door, then work west over the platforms to the research team and report the anomaly. Jump to the south-west tower, clear it, follow the wall down to another walkway and talk to Grist once the others disappear. When she disappears too, take the device from the table.

  • Fast travel door: Research Station. On top of the pillar west of the Cable Car.
  • Key Item: Grist's Tracking Device. On the table after Grist vanishes; it is also one of the mission rewards.
• 5

  Time fluctuations and the four charges

  Two research sites are marked. At the previous one an audio log lies on the ground; at the first one, talk to the researcher Ayad. To restore the power, follow the yellow tape from Ayad, climb the tower and face east. The rooms that sit on the walls shift: change gravity inside them to see the Charge cubes. The stationary main room east of Ayad already has one charged cube; bring it three more, one from the moving room, one from the wall room to its right, and one from the wall room on the east side of the platform, the way Ayad faces. Talk to Ayad again, then go to the third site, "Another Research Site?", where the three researchers show up again.

  • Audio log #1. On the ground at the previous research site.
• 6

  Grist again, and the transmission tower

  In the south-east search area Grist is looking over the edge. After talking to her, check the spot to the west for an anomaly and climb to the upper tower, where a recording lies beside her body. From there go south-east to the Transmission Tower and defend it against waves of Hiss. Check the new time fluctuation, then return east to the Cable Car, talk to Grist, and pull the lever to cross the chasm.

  • Audio log #2. Beside Grist's body on the upper tower.
• 7

  Following the relays to the deepest point

  Off the Cable Car, follow the red beacons, drop down towards the Mold and head south-east to the next anomaly. Use the intercom in the northern room of the research area, then keep following the beacons south-east. In the large open room go right and shift gravity to walk the walls to the exit. Reach Grist, pick up the relay beyond the door, follow the pipes and set it down beside the tree in the last room. Activating it ends the mission.

  • Power Upgrade crate #3. On the left as the Cable Car stops.
  • FBC Taskboard (Underpass). Past the cable car. It only appears once the Central Zone Taskboard is unlocked.
  • Taxi (Underpass). In the large room filled with Mold; it starts The Last Taxi if no other taxi has, and its threshold is a three-stage light-cycle puzzle. Where in the room is disputed; see the note at the foot of the page.
  • Fast travel door: Deepest Underpass. On the right when you reach Grist.

2. The House in Distress

Back to the Oldest House to meet Zoe at Executive Research and reach the Fault there. The Underpass Fault has to be done first: it opens during Recursions and Iterations and needs Reach. Rewards: 1 Living Shard and Sibling Reunion (bronze).

• 1

  Lobby to Prime Candidate Testing

  In the lobby, take the elevator above where Pope stands. A large room further in holds a big group of Hiss. Then take the south elevator towards Executive Research and meet Zoe at the Prime Candidate Testing door. Follow the path to the room with the video displays and talk to Zoe at the Main Observation door to have her open it.

• 2

  Classrooms: the charge and the three patterns

  Go in by the Classrooms door. In the first puzzle room, carry a Charge from the power core on the east side to the one on the south side to open the door. The locked room after it is three core patterns set from the wall controls, in this order:

  • Inverted triangle: top-left, top-right and bottom-middle.
  • Square: the four corners.
  • Cross: the whole middle row, plus top-middle and bottom-middle.

  Then take two Charges back to Zoe's position to restore the power.

• 3

  High Risk Chamber, Director Training and the Main Test Chamber

  Take the High Risk Chamber door on the west side. Before the large room, check the side rooms. At the Director Training door talk to Zoe, clear the Hiss, then go north to the Main Test Chamber and use the TV to enter the Fault.

  • Power Upgrade crate. On the High Risk Chamber path, in a room beside an unmarked room.
• 4

  The ritual

  Inside the Fault it is platforming. Follow the path until you first reach Jesse, turn right and use the TV, then carry on; some surfaces break as you get near them, so keep moving. Interacting with Jesse at the end completes the mission and pops Sibling Reunion.

3. Part 4 Completion

✅ Before Leaving the Oldest House...