CONTROL Resonant Underhill: Location, New Growth & Choices

Dr. Raya Underhill is in her apartment in The Park, northeast of the FBC Base. To reach her during New Growth, question Busken at the base, collect the Level 6 Keycard from her rooftop research site, then search her Central Executive office for the apartment key. Inside the apartment, go upstairs and take the door on the left; Underhill is near the kitchen.

Lab door locked? Take the sewer lab key from the counter near Underhill after speaking with her. The apartment key opens a different door. Busken has no Underhill dialogue? Install 1.4.2 or a later update, fully relaunch, and retry that conversation. Jump to the blocker checks.

What you need right now	Go directly to
Start the quest or find Busken	New Growth starting points
Open the office or apartment	The three keys and their locations
Get into the underground lab	Sewer lab key and entrance
Find the remaining test subjects	Follow every Mold branch
Decide whether to report her or hand over the samples	Underhill choice comparison — story spoilers

Where to find Underhill

The apartment is the NPC destination; the FBC Base and Central Executive are investigation stops. If your objective still asks you to investigate her last known location or office, finish that clue before expecting the apartment door to open.

New Growth route: FBC Base, rooftop research site with Level 6 Keycard, Central Executive office with apartment key, Underhill's apartment with sewer lab key, sewer lab, then back to the apartment.

Our route diagram shows the investigation order and key handoffs, rather than map coordinates. Use the active quest marker for the street route; open the diagram at full size.

Treat the base as your return point while investigating The Park. Search the rooftop site before travelling to Central Executive, and collect the apartment key before travelling back: that sequence avoids two trips to locked doors. PowerPyx's walkthrough documents the route between these stops.

How to start New Growth

There are two documented entry points:

Directly in The Park: speak to the female soldier on the FBC Base rooftop, beside its Fast Travel Door.
Through Zoe: complete Zoe's Briefing at the Watchtower. PowerPyx places that briefing after The Hedron Link, and says it also grants New Growth if you have not already triggered it. Zoe's Briefing requirements.

If New Growth is already in your journal, follow its current objective instead of trying to activate it again. At the questioning stage, find Busken at the FBC Base and ask about Underhill. His lead sends you to the nearby rooftop research site.

You do not need to wait for the campaign credits to try the direct rooftop trigger. Use the quest journal to distinguish a mission that has not started from one that has already advanced past the conversation.

Underhill apartment key and Level 6 Keycard

Three access items appear along the route. Check the name on the locked door before backtracking:

Access item	Where to collect it	What it opens
Level 6 Keycard	Rooftop research site in The Park, with Underhill's Resignation Letter	Her Level 6 office in Central Executive
Underhill's Apartment Key	Desk and documents inside that office	Her apartment in The Park
Key to Underhill's Sewer Lab	Counter near Underhill in the apartment, after the conversation	Underground laboratory door

From the FBC Base, follow the investigation marker south to the rooftop research site. Search the table and collect both the resignation letter and clearance card. Reading the clue and collecting the access item serve different purposes; check that you have done both before leaving.

Fast travel to Oldest House: Central Executive. Go upstairs, turn left, and find the Level 6 office. Search the desk for the Welcome Letter and apartment key, then return to The Park. The apartment walkthrough identifies the office as the key source.

At the apartment building, clear the Mold enemies outside, enter, climb one floor, and use the door on the left. Speak to Underhill in the kitchen. Search the nearby counter for the lab key before leaving.

How to enter Underhill's sewer lab

The lab key comes from the apartment, so searching the sewer tunnels first will leave you at a locked door. After Underhill asks you to recover her test subjects, check for the key pickup on the counter and its inventory notification.

Leave the apartment building, turn left around the corner, and follow the underground objective. In the sewer passage, take the left turn at the junction and unlock the laboratory. This entrance is part of the route between the apartment area and FBC Base; the equipment walkthrough describes the key and lab handoff.

Before following a specimen, finish this room:

Collect the Mold Growth Stimulator and sample tubes from the workbench.
Check that the equipment objective has advanced.
Move beyond the workbench area, drop into the lower passage, and interact with the white, pulsating Mold to begin tracking.

If the door still says a key is required, return to the apartment counter and check the exact key name. If the door opens but the hunt does not progress, check the equipment and Mold interaction instead. Those are different stages of the quest.

How to find all three test subjects

Follow the moving Mold and explore every split in its trail. Reaching one enemy does not finish the hunt. Interact again when the tracking prompt appears, follow the growth until it becomes a test subject, and defeat it before returning to the branch you left.

The Mold tracking walkthrough describes a first fork in the sewer route: the left branch leads to Specimen A, while the other continues toward The Park and splits again for the remaining subjects.

Use this branch checklist to avoid circling the entire zone:

Branch to check	Before moving on
First fork: sewer branch	Defeat its subject, then return to the split
First fork: branch toward The Park	Follow it until the next split
Second fork: first trail	Finish the encounter and collect its sample
Second fork: remaining trail	Finish the last encounter; check for the return objective

If you have two samples, retrace your last unresolved fork instead of searching unrelated Mold events. Once the journal sends you back to Underhill, return to the apartment, rather than the base or office.

Underhill choice: which option should you pick?

For the reward, any of the three options is viable. Joel Franey's GamesRadar guide reports the same quest rewards across the choices, with a later Zoe call reflecting the decision. Choose the outcome that matches how you want Dylan to handle her research.

Story spoilers below. The English dialogue buttons make the sample ownership clearer than shorthand such as “let her escape”:

Dialogue button	What Dylan decides	Pick it if you want to…
I have to report you	Report Underhill to the FBC	Put the decision back under Bureau oversight
Go... without the samples	Let her leave while Dylan retains the samples	Allow her freedom without handing back the experimental material
Take the samples	Give her the samples and let her continue her work	Support her independent research

“Take the samples” is Dylan speaking to Underhill: she takes them. To let her leave while keeping the samples away from her, select “Go... without the samples.” Our recommendation for that compromise is based on the dialogue's meaning, rather than a better loot payout.

GamesRadar lists Brass Dusters and an increase to The Park's Zone Level among the rewards. Check your Artifact inventory and The Gap's crafting options after the turn-in. Its reported effect increases Combat Ability damage by 50% while removing their Falter effects: compare that trade-off with your build before equipping it if you rely on staggering enemies for executions.

For Budding Mycologist, finishing New Growth is only part of the requirement: PowerPyx also lists the Carbon Copy questline. Trophy requirement.

Underhill quest bugs and fixes

Match the symptom to your current objective before repeating the whole route. Remedy confirmed two distinct progression fixes; a missing access item needs a different check.

Symptom	First check	What to try next
Busken offers no Underhill dialogue after quest progression	Installed version and current journal objective	Install 1.4.2 or later, fully relaunch, then revisit Busken at FBC Base
Apartment remains locked	Apartment Key, rather than the Level 6 card	Revisit Underhill's Central Executive office and search its desk
Sewer lab remains locked	Key to Underhill's Sewer Lab	Return to the apartment counter after finishing her conversation
Lab is open but tracking has not begun	Equipment objective and the white Mold	Collect the bench equipment, then interact with the Mold in the lower passage
Subjects are dead but the finding objective remains	Installed version and whether you used the Mold guide	Update and retry the affected save; report the objective if it persists
Only two samples are accounted for	Last trail split you left unexplored	Return to that fork and follow the remaining branch

Cannot ask Busken about Underhill

Hotfix 1.4.2, released October 8, 2026, fixes the missing dialogue after advancing far enough in the quest. Remedy's official notes name this specific condition. After updating and relaunching, load the affected save and check Busken's options against your current journal objective.

If you are already being sent to the office, apartment or lab, continue that objective; the lack of an earlier topic alone does not mean you must restart New Growth.

Test subjects defeated but New Growth will not progress

Update 1.4.0 fixes the finding step remaining incomplete when subjects were eliminated without interacting with the Mold guide. Official 1.4.0 notes. For a fresh attempt, take the lab equipment and begin with the white Mold interaction so you can follow all branches.

For a save already affected, install the current update, fully relaunch, and check the journal again. If it stays blocked, send Remedy support your platform, installed version, exact objective text, sample count, and whether you killed subjects before using the guide. These retry checks are our suggested diagnostic sequence; the patch notes establish which bugs were fixed.

Underhill FAQ

Where is Underhill after I search her office?

Return to The Park and enter her apartment northeast of FBC Base with the apartment key. She is upstairs, through the left-hand door, near the kitchen. Central Executive holds the clue and key.

Do I need to finish the main story first?

Try the direct FBC Base rooftop conversation once you can reach it. PowerPyx documents that start and the Zoe's Briefing route after The Hedron Link. Check the journal first if the quest was already triggered.

Why can I not open the sewer laboratory?

Collect the sewer lab key at Underhill's apartment after the conversation. Check the counter near her: the apartment key and Level 6 card do not open this door.

Which choice lets Underhill leave without the samples?

Go... without the samples. Choosing Take the samples gives them to Underhill. Pick according to the story outcome you want; GamesRadar reports identical quest rewards.

Sources and verification

Checked October 11, 2026. Route and access items were cross-checked against the linked PowerPyx, AllThingsHow and NerdsChalk walkthroughs; choice labels were checked against the dialogue screenshot in Joel Franey's GamesRadar guide. Remedy's official notes establish the 1.4.0 and 1.4.2 fixes. The key comparison, branch checklist, diagnostic table and route diagram are our editorial synthesis, not a claimed hands-on playthrough. See our editorial method; send corrections with your game version to [email protected].

CONTROL Resonant Underhill Guide