This page of our Control guide contains a walkthrough for a side quest called Old Growth. You will learn, e.g. how to reach Dr. Underhill's lab, how to get mold samples, and how to defeat Mold-1 boss.
To start the quest, talk with Emily Pope in Executive Affairs .
Note - Wait until you unlock the Levitate skill. You get it during My Brother's Keeper main quest. Otherwise, you won't be able to access Underhill's lab and Mold-1.
Walkthrough: To get to Dr. Underhill, you need to travel to her lab. To access the lab, you need Levitation. Travel to Central Research in the Research. Below, you will find an abandoned elevator. Jump down and use levitation to get down safely. A little further ahead you will find the Underhill laboratory, who will introduce you to her research.
The woman will instruct you to get five types of mold. Follow the quest marker to reach a large room. Defeat the enemies and start searching for mold.
Type A Mold is found near the checkpoint. There is a corpse behind the tents - follow the path to reach a cave which contains the sought Type A Mold.
This mold grows next to the toilets. Below, next to the pit with poison, you will find a pathway leading to the toilet. You should easily locate the mold.
You will find it a little further, not far from the toilets. You'll reach a TV room - the mold is on the table.
Type D Mold is found below the metal stairs.
A pit with poison and boss Mold 1
Your next objective is to reach a large pit with poison. Go to the area where you found the Mold and enter the pit. Now you have to go through a cave with enemies. Watch out - the exploding mushrooms and enemies encountered in the narrow corridor can cost you a lot of your health points.
Finally, you'll reach the culprit behind all of the Mold in the Office. You'll be facing Mold -1, a powerful boss. The enemy will attack you with tentacles, throw poisonous organisms poisoning you, or drop exploding mushrooms on your head.
The key to victory is constant movement, levitation and quick dodges. Avoid boss attacks and use telekinesis to throw items at the boss' "flower". After the battle, return to Underhill to finish the quest and receive, among others, 4 skill points.
A detailed strategy for the fight with Mold-1 can be found in the Bosses chapter.