The Hiss is the main corrupting presence in Control’s Oldest House, but it’s far from the only one. As you explore you’ll also run into an unpleasant mold that’s spread itself through several compartments of the bureau, and if you want to take it on you’ll need to complete side missions for Dr Underhill. The first missions she’ll offer is Old Growth, asking you to track down Mold samples in the creepy underground area. Your map won’t be much use here, but fortunately for you, we’ve already found all the Old Growth Mold sample locations in Control
Old Growth mold sample locations in Control
To start the Old Growth side mission you’ll need to visit Dr. Underhill. She’s found undeneath the Central Research area. Head to the bottom floor and look for the area smothered by mold. Drop down the hole here (careful on the way down) and make your way through the area to find Underhill. She’ll give you the Old Growth side mission asking you to head deeper and look for five mold samples. Here’s where to find each one.
Type A mold sample location
The Type A mold sample is one of the last you’ll find. It’s near to the fast travel point in the area. There should be a camping site with a tent set up. Head behind the tent and follow the path here to find the Type A mold sample.
Type B mold sample location
You can find the Type B mold sample a short distance from the large main chamber. Take out the enemies and spitting turrets, then make your way to the back right of the room. There’s a large path along the wall here marked with a “Restroom” icon to its right. Enter it then climb up the block with the toilets to your left to find the mold sample in a crevice.
Type C mold sample location
The Type C mold sample location is pretty close to the Type B spot. Keep going down the path past the toilets then turn right at the Lab 05 doorway to find the mold on a table surrounded by televisions.
Type D mold sample location
Keep going along the path, hopping between the pillars and into the Lab 08 door (use evade to cross the gaps). When you reach the metal stairs, take a right and climb up on the boxes then up underneath the stairway to find the mold.
Type E mold sample location
The Type E mold sample is one of the first you can find. It’s right next to the spooky toxic pit in the main room. You’ll need to use evade to boost over to the platform it’s on. Pick it up from the desk here.
Once you’ve delivered all the mold samples, Underhill will ask you to wait a while as she does some research on an antidote. Return later after you obtain the Levitate power and she’ll feed you a pill to protect from the toxic mold. You can now enter the areas you’ve been blocked off from before, including the toxic mold bit you saw earlier here. Underhill will ask you to track down the source of the mold, so make your way back there and float down safely. Be prepared for a pretty tough boss fight through. To beat it, get used to dodging a lot while you hurl objects at the flower head using Launch.
Now that you know the Old Growth mold sample locations you can complete the mission and score yourself a tidy reward of four ability points. If you’re after more, check out our list of all the side missions in Control.