I’ve sent you a message with a guide to this, but I thought it might be something worth posting here as well in case anyone else would find it helpful
Please be aware that spoilers aren’t blurred once you click the arrow!
Guide Here
The short answer is that in order to get to the scene where Nic can reveal they are the other witch, you need to visit Nic’s apartment in the evening in Chapter 6, and then, in the final conversation with Nic, there are a few conversation paths to realize they might be the witch. For every path, you need to have a particular stat above 50, and also have raised a hidden stat by a certain amount, which you can do in a few ways: e.g. by successfully investigating the mysterious tree in the abandoned building, or by successfully researching the map or the legal records in the library earlier in Chapter 6. In theory, you should only need to raise this stat a couple of times, so you don’t need to have found every single clue. I can give a more detailed walkthrough for this if anyone is interested, I just haven’t had the time yet to write one up in full, so for now I’m focusing on getting through the conversation in Chapter 6.
Here are some of the conversation paths to find out the truth (all of these are in the final conversation you can have with Nic in Chapter 6, after they have woken up):
"I want to ask Nic about the spray paint.* OR *I want to ask Nic about the strange twigs in the snake tank.* OR *"Why do you have leaves in your bag?" Is there something unusual about them?*
(One of these options will appear depending on what you find in Nic’s apartment)
Then, in the next choice:
-“If what doesn’t work?” I frown, confused.
For this, precision must be over 50. If it is, you will get one of these two dialogue options in your next choice, depending on your earlier choices in Nic’s apartment:
-“Did you vandalize the sculpture in the park?”
OR
“Did you put the tree in that abandoned building?”
If you get the first one, your influence will need to be over 50. If it is, pick this option in your next choice:
-I don’t think I can trust (them) unless I know why (they) did it. Even if it ends badly, I have to ask.
If you pick this option, you’ll be taken to the next part of the scene, and you’ll be on the right path to find out the truth. You just need to make sure you go and see Nic the next morning, in Chapter 7.
If you get the second one (“Did you put the tree in that abandoned building?”), your precision will need to be over 50, which it already is if you chose this path and reached this point. In that case, you’ll be taken to the next part of the scene, and you’ll be on the right path to find out the truth. You just need to make sure you go and see Nic the next morning, in Chapter 7. (I think in hindsight it was a mistake on my part to test the same stat here twice - I will ask the game’s editors about possibly changing this.)
I'll ask Nic if (they) saw that metal box in the forest. Maybe (they know) what it is?
Then, in the next choice:
“Really deep in the forest. It’s pretty hidden away.” I’ll keep things vague just in case, but I’m curious enough that I want to keep asking questions.
OR
“Right around a grove of hemlock trees, just a little east of the river.” I don’t mind being specific; I really want to know what Nic knows.
If you pick Really deep in the forest, both ecology and witchcraft must be over 50. This is because this is the “vague” option, so the stat test is a little harder.
If you pick Right around a grove of hemlock trees, only ecology must be over 50.
If your stats are right, you’ll be taken to the next part of the scene, and you’ll be on the right path to find out the truth. You just need to make sure you go and see Nic the next morning, in Chapter 7.
I'll ask Nic what (they've) been doing with (their) late nights. (Are they) partying, or (do they) have a cool secret project?
Then, in the next choice:
I’ll ask (them) what the coolest thing is to see at night. Maybe I should try it.
OR
I’ll ask (them if they) happened to walk past the building that had the fire the other night. Maybe (they) saw something?
OR
I’m suddenly reminded of what happened last night in the park. I tell Nic about it, wanting to get if off my chest.
OR
I’ll ask if (they) ever (get) scared. I’d be a little worried if I were walking around after dark.
For all of these options, the stat check is the same - precision must be over 50. (From there, it follows the same route as in the first bullet point above.)
-“Did you vandalize the sculpture in the park?”
OR
“Did you put the tree in that abandoned building?”
If you get the first one, your influence will need to be over 50. If it is, pick this option in your next choice:
-I don’t think I can trust (them) unless I know why (they) did it. Even if it ends badly, I have to ask.
If you pick this option, you’ll be taken to the next part of the scene, and you’ll be on the right path to find out the truth. You just need to make sure you go and see Nic the next morning, in Chapter 7.
If you get the second one ("*Did you put the tree in that abandoned building?*"), your **precision will need to be over 50**, which it already is if you chose this path and reached this point. In that case, you'll be taken to the next part of the scene, and you'll be on the right path to find out the truth. You just need to make sure you go and see Nic the next morning, in Chapter 7. (I think in hindsight it was a mistake on my part to test the same stat here twice - I will ask the game's editors about possibly changing this.)
"I want to ask Nic about the spray paint.* OR I want to ask Nic about the strange twigs in the snake tank. OR “Why do you have leaves in your bag?” Is there something unusual about them? I’ll ask Nic if (they) saw that metal box in the forest. Maybe (they know) what it is? I’ll ask Nic what (they’ve) been doing with (their) late nights. (Are they) partying, or (do they) have a cool secret project?
If you follow one of these paths, you should get the option to go and see Nic the next morning, in Chapter 7. That’s where you’ll find out the truth, so make sure to go and see them then.
I tried to check through the code as carefully as I could, but it’s possible I made a mistake somewhere, so if you can’t get one of these paths to work then please let me know. If I haven’t explained something clearly enough, or you’d like to ask anything else, let me know as well!
On a separate note, I’ve spent some time writing up a small retrospective of the game, laying out some of the things that I’ve learned and might do differently next time as well as addressing some of the most common feedback I’ve seen about the game. I’m planning on posting it here quite soon, but it anybody has any questions or comments they’d like me to respond to, let me know and I’ll add them to the write-up