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.
寻找 / 跟随研究小队
留在 Recursions and Iterations。
攀爬 The Spire / Resonant
那是可选任务 The Underpass Resonant，不是这条主线。
打开 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，去追研究队。
Evacuation Zone 下方的自助洗衣店
需要完整的 Sinkhole 路线？去看区域攻略，而不是反复读这一页。
第一次下到 Underpass。经过的每一个快速旅行门都激活。
第一段下降路线之上的 The Spire
如果不确定该往哪走，就跟着悬挂的白色工作灯，而不是靠罗盘方向。
Activate these fast-travel doors as you pass. They are your safety net if the Reach gate sends you away.
激活 Sinkhole 快速旅行门
激活 The Spire 快速旅行门
出发去拿 Reach 之前，先激活 Halfway Trail。
在到达 research site 之前如果不确定方向，就跟着悬挂的白色工作灯。
离开之前先激活 Deepest Underpass 的快速旅行门。
Before leaving for Reach, activate Halfway Trail.
沿考察路线前往 beacon 和研究站。
Halfway Trail 缺口对面的 beacon
如果缺口对面有一个发光的 Reach Point，说明你撞上了设计好的 Reach 门槛。
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.
同一批研究员会以不同的时间状态出现。判断哪个站点才是当前进度。
研究平台和它上面的塔
人物反复出现和消失是这个任务的时间异常，不是 NPC 坏了。
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: 当前
Expected quest event: 之后
Expected quest event: 更早
塔 / 供电室
小队平台
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.
把三个 charge 搬回 Ayad 的供电室，然后追踪小队和 Grist。
Ayad 的中央供电室
charge 一旦拿起就有时间限制：直接返回，不要顺手探索。
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.
会移动 / 变化的房间
直接把它搬回中央供电室。
另一侧的墙边房间
走最直接的路线回中央房间。
东侧低层区域
不要绕路；charge 有时间限制。
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，然后回到缆车跨过深沟。
你之前经过的 Cable Car
如果过不去，先完成 Transmission Tower 的目标。
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.
沿红色 beacon 抵达最深处，并放置最终的 probe relay。
Deepest Underpass 的那棵树
在最后的重力房间里，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.