Control Resonant: New Growth Walkthrough and Doctor Underhill Choice Explained

New Growth is a post-story quest in Control Resonant that sends Dylan into an increasingly uncomfortable dispute between the Federal Bureau of Control and Doctor Underhill, a Mold researcher who has vanished from official oversight. The assignment begins as an investigation into her disappearance, but develops into a hunt for experimental test subjects and ends with a decision over whether Underhill should face the FBC, flee, or lose access to her research samples.

The good news for players worried about locking themselves out of rewards or future content is that the Underhill decision does not appear to create lasting gameplay consequences. The choice changes the outcome Dylan recounts to Zoe, including her reaction, but the quest reward and regional progression are the same regardless of which response is selected.

Here is a full route through New Growth, including the key items needed to advance, how the wandering Mold trail works, and what to expect from the final conversation.

How to unlock New Growth

New Growth becomes available only after completing the main story. Once the campaign is over, return to the Watchtower and speak with Zoe again. She introduces the situation surrounding Doctor Underhill, an FBC scientist whose work focused on the Mold before she went missing.

For useful background on this topic, read Songs of Glimmerwick Launches on Steam, Bringing Musical Magic to a Woodland University.

This is not simply a missing-person case. As the quest progresses, it becomes evident that Underhill's work has continued outside normal FBC channels. That tension is central to the final choice, so it is worth reading the documents collected during the investigation rather than treating them as optional background material.

New Growth walkthrough

Ask about Underhill at the FBC base

After accepting the quest from Zoe, travel to the FBC Base in The Park. Speak with the guard named Busken and ask about Doctor Underhill. Busken points Dylan toward a nearby rooftop, which serves as Underhill's last known location and the next objective.

This opening step is straightforward, but it establishes the route through the quest: first gather traces of Underhill's departure, then follow those clues through the Oldest House and back into The Park.

Search Underhill's last known location

Head to the rooftop indicated by Busken. On the roof, inspect Underhill's desk and collect both required pieces of evidence:

• Level 6 Clearance Keycard
• Resignation Letter

Make sure to pick up both items before leaving. The keycard is needed for the next stage, while the letter provides important context for Underhill's break with the FBC. The combination of an access credential and a resignation message makes it clear that this is not an ordinary disappearance.

Visit Central Executive in the Oldest House

With the rooftop evidence in hand, go to the Oldest House and make your way to Central Executive, the area containing the Fast Travel Door. The Level 6 clearance allows access to the relevant room there.

Inside, find Underhill's Apartment Key along with additional notes. As with the resignation letter, these notes help explain why Underhill is pursuing her work independently. They also point the investigation back toward The Park, where her apartment building can be reached.

If the objective seems stalled at this point, check that the apartment key has been collected rather than only reading the material in the room. The key is the important progression item for the next location.

Clear the Mold outside Underhill's apartment

Return to The Park and locate Underhill's apartment building. The entrance is obstructed by Mold, so clear the growth outside before trying to continue inside. Once the blockage is dealt with, enter the building and find Doctor Underhill.

The encounter confirms that she is alive and still actively conducting experiments. Underhill asks Dylan to assist by gathering material from test subjects, shifting the quest from an investigation into a practical field assignment.

At this stage, the disagreement between Underhill and the FBC becomes more explicit. The FBC is concerned that she could make an already dangerous Mold situation worse, while Underhill believes the Bureau's caution prevents meaningful progress. New Growth does not demand that players decide who is morally right immediately, but it does begin building the case for the decision to come.

Pick up the test equipment in the sewers

Before test subjects can be tracked, retrieve the necessary Test Equipment from the laboratory in the sewers. Follow the quest marker to the lab and collect the equipment there.

Once equipped for the task, Dylan can begin following the unusual white Mold growth that leads toward the subjects. This portion can be slightly confusing because the trail is not always a single uninterrupted route.

How to find all three test subjects

The test-subject search revolves around white Mold. Trigger the growth when you encounter it, then follow it as it moves away. It functions as the trail to your targets rather than as an enemy to eliminate immediately.

The key detail is that the white Mold can split into two separate directions. When that happens, do not assume one branch is a decoy. Follow every available route. New Growth requires finding all three test subjects, and ignoring a split path can leave Dylan one target short with no obvious indication of where progress was missed.

When a subject is located, defeat it to register the objective. Repeat the tracking process until all three have been eliminated.

1. Trigger a patch of white Mold.
2. Follow its movement through the environment.
3. At any branching point, investigate both directions.
4. Find and defeat the test subject at the end of each trail.
5. Continue until the quest tracker confirms all three subjects are complete.

Players who lose the trail should pause and consult the in-game map and current objective area before retracing their steps. The important rule remains the same: every branch matters. The quest's tracking mechanic is designed to lead to multiple targets, not just one.

Return to Underhill and make the final decision

After all three subjects have been dealt with, return to Underhill at her apartment. The conversation now moves beyond the immediate experiments. Dylan has enough information to understand that Underhill is operating without FBC authorization, and that the Bureau is actively worried about the risks of her research.

The final selection gives Dylan three broad ways to resolve the situation:

• Report Underhill to the FBC.
• Allow Underhill to escape and continue on her own terms.
• Let Underhill escape but retain the samples, preventing her from continuing the experiments with them.

It is framed as a difficult call because each option reflects a different judgment. Reporting her supports institutional oversight, but potentially ends research that Underhill believes is necessary. Letting her go prioritizes her expertise and independence, while carrying the obvious danger of enabling unsanctioned experimentation. Letting her leave without the samples sits between those two positions: Dylan does not hand her over, but does restrict her ability to proceed.

What is the best Underhill choice?

From a gameplay standpoint, there is no single best answer. The Underhill choice has no known long-term gameplay consequence. It does not alter the quest reward, does not change The Park's regional progression, and does not appear to create a different ongoing mission path.

After the decision, Dylan speaks with Zoe and tells her what happened. Zoe responds with an opinion shaped by the choice made, so players interested in role-playing Dylan may want to select the option that best fits their view of Underhill, the FBC, and the risks of Mold research.

For everyone else, choose freely. There is no indication that one option produces superior gear, access, or future content.

New Growth rewards

Completing New Growth grants the same rewards regardless of the outcome chosen for Doctor Underhill:

• Brass Dusters artifact
• An increase to The Park's Zone Level

The Brass Dusters come with a major combat tradeoff: combat abilities deal 50% more damage, but they no longer apply Falter effects. That makes the artifact a potentially strong option for aggressive builds focused on maximizing ability damage, especially if Falter is not central to the player's usual combat approach.

However, the loss of Falter means it may not fit every build. Players who rely on the status effect for control, setup, or combat rhythm should consider whether the damage increase outweighs the missing utility. As a reward, it reinforces the quest's wider theme of accepting risk in pursuit of greater results.

New Growth checklist

• Finish the main story.
• Speak to Zoe again at the Watchtower.
• Ask Busken about Underhill at the FBC Base in The Park.
• Search the rooftop and take the Level 6 Clearance Keycard and Resignation Letter.
• Go to Central Executive in the Oldest House.
• Open the relevant room, collect Underhill's Apartment Key, and read the notes.
• Clear the Mold outside Underhill's apartment building in The Park.
• Speak with Underhill.
• Collect Test Equipment from the sewer laboratory.
• Follow every white Mold trail and branch to find all three test subjects.
• Defeat each subject.
• Return to Underhill and select any of the three final outcomes.
• Collect the Brass Dusters and The Park Zone Level increase.

New Growth may present its finale as a major ethical fork, but players do not need to stress over hidden mechanical penalties. The decision is primarily about narrative preference, while the practical challenge lies in properly tracking each white Mold branch and ensuring all three test subjects have been found.