Start New Growth in The Park
Complete Zoe’s Briefing for the automatic lead, or speak to the soldier beside the FBC Base rooftop travel door in The Park. Ask the staff about Underhill to advance to her last known location. Activate that travel door for the return trips.
To reach the rooftop, power the base elevator or approach from the northeast sewer route, emerge east of the base and cross to the roof. The direct base conversation is an alternative start; the Watchtower route is not the only trigger.
Collect the three access items in order
| Where | Take this | What it opens |
|---|---|---|
| Research roof south of FBC Base | Level 6 Keycard + Resignation Letter | Underhill’s Central Executive office |
| Oldest House: Central Executive, Clearance 06 office | Underhill’s Apartment Key | Her apartment in The Park |
| Apartment kitchen counter, after speaking to Underhill | Key to Underhill’s Sewer Lab | The locked lab in the sewers |
Follow the search marker south of the base to the smaller research roof and inspect its table. In Central Executive, go upstairs / left to the Level 6 office and search the desk. Return to the upper/northeast part of The Park, clear the Mold at the marked building, go up one floor and enter the apartment on the left.
Do not leave with only the conversation completed. Speak to Underhill in the kitchen, then pick up the lab key from the counter. A locked sewer-lab door usually warrants checking this pickup first.
Take the equipment and activate the Mold trail
Follow the lab marker into the sewer between the apartment and FBC Base. Use the lab key, turn left through the crossing and enter the research room. Collect the quest-marked equipment and Sample Tubes from the tables before dropping beyond the railing.
At the white Mold, use the tracking interaction when it appears. Follow the moving trail rather than attacking an unactivated patch or guessing a specimen’s location.
Follow every branch and defeat three specimens
The trail splits. Track one branch to its enemy, defeat that specimen and collect its sample, then return for the branch you left behind. The route toward The Park splits again; both ends matter.
| Target | Search area |
|---|---|
| Specimen A | Deep sewer enclosure |
| Specimen B | Sewer courtyard |
| Specimen C | Back alley reached via the rooftop route |
Use the trail and quest markers to distinguish the branches. You need all three specimens, not just the first fight. Fire abilities help against Mold if they are available in your build. Once the objective changes to Return to Underhill, go back to her apartment.
Found the enemies but the search objective remains? Remedy’s 1.4.0 update fixes New Growth failing to progress when test subjects were killed without interacting with the Mold guide. Check your installed version and use the guide interaction during the route; the notes do not promise how every older affected save recovers.
Return, choose an ending, and check completion
Finish the conversation with Underhill to close the quest. You can report her to the FBC, let her leave with her samples, or let her leave while keeping the samples. The reported outcome changes Underhill’s fate and the later conversation with Zoe; the published walkthroughs agree that the quest rewards stay the same.
Completion grants Untapped Brass Dusters and progress toward Budding Mycologist. That achievement also requires the Carbon Copy questline. Finishing New Growth alone is not a guarantee that the trophy will appear.
Check the quest’s completion banner or completed Quest Log entry after the final dialogue.
Return to Underhill · 10:42 ▶Your investigation checklist
Saved in this browser. These ticks do not change your game save.
Watch the full Underhill route
Sources & image credits
Walkthrough sources, version notes & image credits
- PowerPyx — alternative rooftop trigger, objective order and Carbon Copy trophy requirement.
- GamesRadar+ — keycard, sample branches and ending choices.
- ShowGamer — lab key and three-specimen route.
- WoW Quests video — full 11:29 route, key and Mold interaction samples.
- Remedy 1.4.0 update — Find the Test Subjects progression fix.
Checked October 7, 2026. Gameplay footage is from the launch period; the displayed game build is not identified. Version changes below come from Remedy’s 1.4.0 notes. Selected frames retain the creator’s on-screen marks.