CONTROL Resonant

Main story · Contain the Crisis

Find the research team below the Sinkhole

Recursions and Iterations

Underpass · Main story #7

Follow Pope's missing research team beneath the Sinkhole, investigate the time fluctuations, and push deeper into the Underpass. Midway you need Reach, then you restore power for Ayad, find Grist, cross the chasm and place the final probe relay.

Find my current step
  • Underpass
  • Reach required midway
  • Long-form main quest
Route statusPhase 1 of 7

Phases are states, not a checklist. Track the one you are in and the page keeps your resume point.

Quest at a glance

Questline
Contain the Crisis
Previous
Enemy of My Enemy
Starts
Oldest House Lobby
Main region
Underpass
Mid-quest gate
Reach
Reach quest
The Subway Fault
Key characters
Pope · Grist · Ayad
Key mechanic
Time fluctuations
Major puzzle
Restore the power
Major combat
Transmission Tower
Final objective
Place the final probe relay
Next story quest
The House in Distress
Mid-quest requirement

You will need Reach to finish this mission.

Don't have Reach? Complete The Subway Fault first.

Get Reach
How the pause works
  1. Start Recursions and Iterations at the Oldest House
  2. Enter the Underpass and follow the research route
  3. Progress partway, to the Reach gate
  4. Complete The Subway Fault if you still need Reach
  5. Return to Halfway Trail and continue

This is not a quest-start requirement

You can start and play a large part of Recursions and Iterations before Reach. The gate sits partway through, near Halfway Trail.

Which objective are you actually following?

The Underpass runs several quest lines at once. If a guide says go east but your marker points west, you are probably on a different quest.

You are here

Find / follow the research team

Stay on Recursions and Iterations.

Switch to this quest

Investigate Jesse / a Fault

That objective belongs to a different quest line.

Open The Underpass Fault
Switch to this quest

Climb the Spire / Resonant

That is the optional Underpass Resonant, not this main story.

Open The Underpass Resonant

Quest state navigator

You are not collecting twelve objectives. Find the phase you are in, then follow that section.

Return below the Sinkhole

Pope sends you back beneath the Sinkhole toward the research expedition.

You are here
Route
  1. Return to the Oldest House
  2. Head to the Evacuation Zone laundromat
  3. Enter Personnel Access and follow the yellow tape
  4. Drop through the lower chambers
  5. Activate the Sinkhole fast-travel door
  6. Continue downward
Landmark

The laundromat below the Evacuation Zone

If you are stuck

Need the full Sinkhole route? Open the location guide instead of re-reading this page.

Journal objectives
  • Meet Pope
  • Return below the Sinkhole

Enter the Underpass

First descent into the Underpass. Activate every fast-travel door you pass.

Route
  1. Follow the hanging white work lights
  2. Reach the research route
  3. Activate The Spire fast-travel door
Landmark

The Spire, above the first descent

If you are stuck

If you are unsure where to go, follow the hanging white work lights rather than a compass direction.

Journal objectives
  • Enter the Underpass
  • Reach the research route
Underpass checkpoints

Activate these fast-travel doors as you pass. They are your safety net if the Reach gate sends you away.

  • Activate the Sinkhole fast-travel door

  • Activate The Spire fast-travel door

  • Before leaving for Reach, activate Halfway Trail.

  • When you are unsure where to go before the research sites, follow the hanging white work lights.

  • Activate the Deepest Underpass fast-travel door before you leave.

Before leaving for Reach, activate Halfway Trail.

Find the research team

Follow the expedition route toward the beacon and the research site.

Route
  1. Leave The Spire for the Halfway Trail
  2. Pass the Reach gate near the Halfway Trail
  3. Reach the beacon
  4. Enter the research site
  5. Find the research team
Landmark

The beacon beyond the Halfway Trail gap

If you are stuck

If a glowing Reach Point sits across a gap, you have hit the designed Reach gate.

Journal objectives
  • Find the research team
  • Reach the beacon
The Spire

Main story: keep following the research-team route.

Optional branch: The Underpass Resonant.

It becomes available once you reach the Underpass, but it is not a hard requirement for this quest.

Open The Underpass Resonant
Route blocked? The Reach gate

Near the Halfway Trail the route jumps across a gap. If you see a glowing Reach Point on the far side, Reach is required here.

Do you see a glowing Reach Point across the gap?

Return to

Recursions and Iterations · Halfway Trail

Continue main quest
Complete The Subway Fault

The mission is not bugged or softlocked. Reach is a designed progression gate.

Reach the beacon

Once Reach is unlocked, cross the gap and follow the marker to the beacon and the research site.

Underpass navigation language
  • White — research expedition route

    Before the research sites: follow the hanging white work lights.

  • Red — late relay route

    After the Cable Car: follow the red relay beacons.

Investigate the time fluctuations

The same researchers appear in different time states. Work out which site is current.

Route
  1. Read who is at each research site
  2. Check the objective marker, not the faces
  3. Follow the fluctuation the journal points to
Landmark

The research platform and its tower

If you are stuck

People appearing and disappearing is the quest's time anomaly, not a broken NPC.

Journal objectives
  • Investigate the research site
  • Check the time fluctuation

Research sites and time states

The same researchers appear more than once in different time states. That is the quest, not a bug.

Do not name them Site 1, 2, 3. Read who is here, what the objective is, and which landmark you are standing at.

Time state

Ayad site

Who is here
Ayad
Current objective
Power problem
Key landmark
Tower / power room

Expected quest event: Current

Time state

Grist site

Who is here
Research team
Current objective
Team anomaly
Key landmark
Team platform

Expected quest event: Later

Time state

Earlier site

Who is here
Earlier team
Current objective
Audio / fluctuation
Key landmark
Near the Cable Car

Expected quest event: Earlier

Time fluctuations

  • Tower / power room

  • Team platform

  • Near the Cable Car

This is not a collectible list. It helps you understand why the same people keep appearing and disappearing.

When you are unsure where to go before the research sites, follow the hanging white work lights.

Restore power and find Grist

Bring three charges back to Ayad's power room, then track the team and Grist.

Route
  1. Find the central power room near Ayad
  2. Carry the three charges back to it
  3. Return to Ayad
  4. Locate Grist
Landmark

Ayad's central power room

If you are stuck

Charges are time-limited once picked up: go straight back instead of exploring.

Journal objectives
  • Restore the Power
  • Return to Ayad
  • Locate Grist

Restore the power

Bring every charge to the same central room near Ayad. Do not power the outlying rooms.

Main room cores1 / 4 powered
  • Core A
  • Core B
  • Core C
  • Core D

Need 3 more charges

Bring every charge to the same central room near Ayad. Do not power the outlying rooms.

Power restoration map

Schematic of the rule, not a live readout.

Core
  • Source 1Core B

    Shifting / moving room

    Carry it straight back to the central power room.

  • Source 2Core C

    Wall room on the far side

    Take the most direct line back to the central room.

  • Source 3Core D

    East-side lower area

    Do not detour; the charge is time-limited.

Carrying a charge? Go straight back to the power room. Don't explore while holding it.

Return to Ayad

When all four cores are powered, talk to Ayad. The world state then changes and the researchers move again.

People moving and disappearing here is the quest's time anomaly, not a broken NPC.

Locate Grist

Quick route

  1. Head to the research site southeast of the power room
  2. Cross to the edge of the platform
  3. Follow the objective marker to Grist

What you find there is a story spoiler.

Transmission Tower and the chasm

Defend the tower, then return to the cable car to cross the chasm.

Route
  1. Reach the Transmission Tower
  2. Defend it until the objective changes
  3. Return to the Cable Car
  4. Use the lever to cross the chasm
Landmark

The Cable Car you passed earlier

If you are stuck

If you cannot cross, finish the Transmission Tower objective first.

Journal objectives
  • Defend the Transmission Tower
  • Cross the chasm

Transmission Tower

What happens

A wave defence. Hold the tower until the objective changes.

Recommended

Prepare healing and crowd control before you start.

Success

The objective changes to the next fluctuation.

Exact enemy composition is not mapped here yet; the page does not guess from nearby encounters.

Cross the chasm by Cable Car

Remember the Cable Car you passed earlier? Go back to it now and use the lever to cross.

I can't cross the chasm
  • Are you at the Cable Car? → No — head back to the Cable Car first.
  • Have you completed the Transmission Tower? → No — finish that objective first.
  • Then use the Cable Car lever.

Follow the relays and finish

Follow the red beacons to the deepest point and place the final probe relay.

Route
  1. Follow the red relay beacons
  2. Cross the altered research area
  3. Clear the gravity room
  4. Reach the Deepest Underpass
  5. Place the final probe relay
Landmark

The tree at the Deepest Underpass

If you are stuck

In the final gravity room, do not aim straight for the exit.

Journal objectives
  • Follow the relays
  • Place the final probe relay
Follow the relays

After the Cable Car, follow the red relay beacons through the altered research area.

After the Cable Car, follow the red relay beacons.

Final gravity room
  1. Don't aim straight for the exit
  2. Go right first
  3. Shift gravity and follow the wall route
  4. Reach the far-side exit
Final probe relay
  1. Reach the Deepest Underpass
  2. Pick up the final relay
  3. Follow the pipes
  4. Reach the tree
  5. Place and activate the relay

Don't skip: Activate the Deepest Underpass fast-travel door before you leave.

Quest complete

Next main story: The House in Distress

Other Underpass content

Into the Valley of Death

A side story unlocked around this stage. It does not block the main mission.

The Underpass Resonant

Available at The Spire once you reach the Underpass. Optional, not a hard prerequisite.

The Underpass Resonant

Recursions and Iterations troubleshooter

What's happening?

How many cores are powered in the main room?
  • 1 — find all three charges.
  • 2 — two charges remaining.
  • 3 — one charge remaining.
  • 4 — return to Ayad.
None of these? Open the Quest Troubleshooter
What next?

Continue the main story

Recursions and Iterations leads straight into the next main story quest.

Stuck on this quest?

Tell the assistant which phase you are in and what you see. It knows the Reach gate, the power cores and the cable car.

Ask about this quest →
Where this page sits

This quest page owns the Recursions and Iterations steps. Progression order lives in the walkthrough.

Browse all questsOpen the progression walkthrough
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