Main story · Contain the Crisis
Find the research team below the SinkholeUnderpass · 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.
Phases are states, not a checklist. Track the one you are in and the page keeps your resume point.
You will need Reach to finish this mission.
Don't have Reach? Complete The Subway Fault first.
Get ReachThis 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.
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.
尋找 / 跟隨研究小隊
留在 Recursions and Iterations。
攀爬 The Spire / Resonant
那是可選任務 The Underpass Resonant，不是這條主線。
開啟 The Underpass ResonantYou are not collecting twelve objectives. Find the phase you are in, then follow that section.
Pope 把你重新送回 Sinkhole 下方，去追研究隊。
Evacuation Zone 下方的自助洗衣店
需要完整的 Sinkhole 路線？去看區域攻略，而不是反覆讀這一頁。
第一次下到 Underpass。經過的每一個快速旅行門都啟動。
第一段下降路線之上的 The Spire
如果不確定該往哪走，就跟著懸掛的白色工作燈，而不是靠羅盤方向。
Activate these fast-travel doors as you pass. They are your safety net if the Reach gate sends you away.
啟動 Sinkhole 快速旅行門
啟動 The Spire 快速旅行門
出發去拿 Reach 之前，先啟動 Halfway Trail。
在到達 research site 之前如果不確定方向，就跟著懸掛的白色工作燈。
離開之前先啟動 Deepest Underpass 的快速旅行門。
Before leaving for Reach, activate Halfway Trail.
沿考察路線前往 beacon 和研究站。
Halfway Trail 缺口對面的 beacon
如果缺口對面有一個發光的 Reach Point，代表你撞上了設計好的 Reach 門檻。
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 ResonantNear 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?
The mission is not bugged or softlocked. Reach is a designed progression gate.
Once Reach is unlocked, cross the gap and follow the marker to the beacon and the research site.
Before the research sites: follow the hanging white work lights.
After the Cable Car: follow the red relay beacons.
同一批研究員會以不同的時間狀態出現。判斷哪個站點才是目前進度。
研究平台和它上面的塔
人物反覆出現和消失是這個任務的時間異常，不是 NPC 壞了。
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.
Expected quest event: 目前
Expected quest event: 之後
Expected quest event: 更早
塔 / 供電室
小隊平台
Cable Car 附近
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.
把三個 charge 搬回 Ayad 的供電室，然後追蹤小隊和 Grist。
Ayad 的中央供電室
charge 一旦拿起就有時間限制：直接返回，不要順手探索。
Bring every charge to the same central room near Ayad. Do not power the outlying rooms.
Need 3 more charges
Bring every charge to the same central room near Ayad. Do not power the outlying rooms.
Schematic of the rule, not a live readout.
會移動 / 變化的房間
直接把它搬回中央供電室。
另一側的牆邊房間
走最直接的路線回中央房間。
東側低層區域
不要繞路；charge 有時間限制。
Carrying a charge? Go straight back to the power room. Don't explore while holding it.
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.
Quick route
What you find there is a story spoiler.
守住 tower，然後回到纜車跨過深溝。
你之前經過的 Cable Car
如果過不去，先完成 Transmission Tower 的目標。
A wave defence. Hold the tower until the objective changes.
Prepare healing and crowd control before you start.
The objective changes to the next fluctuation.
Exact enemy composition is not mapped here yet; the page does not guess from nearby encounters.
Remember the Cable Car you passed earlier? Go back to it now and use the lever to cross.
沿紅色 beacon 抵達最深處，並放置最終的 probe relay。
Deepest Underpass 的那棵樹
在最後的重力房間裡，不要直接朝出口走。
After the Cable Car, follow the red relay beacons through the altered research area.
After the Cable Car, follow the red relay beacons.
Don't skip: Activate the Deepest Underpass fast-travel door before you leave.
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 ResonantWhat's happening?
Recursions and Iterations leads straight into the next main story 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 →This quest page owns the Recursions and Iterations steps. Progression order lives in the walkthrough.