If anyone is confused about how to get the Forbidden Truth badge. Here's how.
Go in the potion making room and turn on the lanterns as it will open a secret door. Once all the lanterns are lit up, walk back to the entrance of the potion room as there's a secret room and you can make a secret potion which there's a note "This cauldron has access to forbidden ingredients."
Put the potions in order
Once you have the badge, go to the Chapter 2 tunnel area and there will be a boarded up door which there will be a new cutscene.
Cleo