I will start the guide with general info, then become more specific over time. This means as you scroll down there will be more spoilers both marked and unmarked. Even high level detail can be considered spoilers to some, so if you feel that way it might be better to look elsewhere for specific help

I only wrote out the parts that stood out to me as most important so far. I will likely contribute more as requested or I get free time. Publishing early for anyone who is stuck on these parts and wants help.

Many people are linked together, meaning you cannot progress one investigation without progressing the other first. These might be obvious or not revealed until later. If you can't think of how to progress someone and you have another person to investigate just swap over.

How to spend your time

• It is always a good idea to ask people when you first meet them their time table for the event. Finding people is a hassle. Depending on the person there might be other schedules around that help
  
• If you have access to someone's room, prioritize investigating it (once they are not in it)
  
• When discussing with people, stick to evidence unless you have a specific person you want info on for a high level investigation
  
• When discussing with people, you do not need to ask about everything. You should only ask if you are unsure on what to investigate next. (You can always quick save and ask and if it doesn't provide information load, but it shouldn't be needed unless you are curious)
  
• You should only need to research the topics found in books on the research desk, the rest of the library is for your own education if you don't know the source material

About the occult diagrams:
If you do not have the ability to see the background lines, it is practically impossible to guess the pattern. Come back later

About locked containers:
About 2/3 of locked containers have the clue within the room. The others are usually not too far away. I know of 3 exceptions to this

Investigation Map:

• If a connection is green you are probably done with it
  
• Orange means you have gotten partial information, you might need to find something new or solve a puzzle
  
• Grey means you don't know, most of the time you can treat this the same as orange, but it might mean you are blocked until you do something else

Real world time to complete the game: 14 hours

• I was able to complete all mysteries in one playthrough without assistance
  
• In that run I finished with 2.5 hours of time left, or about 150 extra interactions
  
• About final outcome: I saved everyone with a preventable death
  
• About final outcome: You are not locked out of alternate endings, you can load your last save and make a different choice to immediately get its ending (except 1)

If you are terrible at these diagrams here is some help.

1. Look for any nodes with an odd number of edges, this means you MUST either start or end there.
1b. This means if you have a diagram with more than 2 of these, something is wrong
2. Try to fill out loops of all even nodes, so that you can solve the puzzle in stages

If you really struggle, these are called "eulerian paths"
Here is a solver https://graphonline.top/en

Click add vertex and put in all the dots.
Click connect vertex and add in undirected paths
Click algorithms and select "eulerian path"

This area has its door sealed, and will not open during the events of the game.

1st hint: What is nearby on the map?
2nd hint: In that location, is there anything odd?
3rd hint: Miss Deane has the solution to the puzzle

What to do inside:
1: If you found an item while on The Trail, it can be used here. Hint on where to get that item below
1b: If you didn't find the locker key, its on The Trail in the Maze
2: You can encounter 2 people trying to have a secret meeting here. This is required for one of their investigations to progress
3: Some other people sneak in at times, but they don't offer any investigation progress that I could tell

General tips

• If you do not yet have access to someone's room, it is likely not worth investing your time in them yet
  
• Each detail of the culprit revealed is likely to only remove a couple people

Slightly spoiler tips

• To get the religion of a lot of people, attend both services
  
• To get the shoe size of people, check their rooms. Only the shoes matter not the clothes

Point of no return number of un-eliminated culprits:
When you are about to go to the final area you will get a warning. At this point you should have narrowed it down to just 2 people. One due to not having any information on them.

You do not need to look at each piece of the trail, you should look at least 1 item in each map section.

There are 2 items to pick up on the trail, one is usable later

The person who had The Fight might not be related to other investigations. Don't confuse them with the person from The Trail

The investigation shows a line to each person:

• Grey means you haven't learned anything
  
• Orange means you have a possible explanation
  
• Green means you confirmed them not being involved, no need to talk to them about it any more

Most people can provide information if you bring up The bridge game

If they reference someone else, you can go confirm with them to turn orange to green

If they reference a location, try investigating that location.
Locations:
Library: Look at the armchairs

You cannot enter this until Day 3. This blocks off certain investigations.

You must enter from near the stables, but once you progress a bit and get a key you can leave and return through the West Tower.

2 people will block off part of the area, you can explore a few rooms but not complete your investigation until they are gone.
Ward comments when you finish a room in the basement. This should be reflected in the investigation summary.
The laundry will show as incomplete until you can get to an area where you need to make a cleaning solution

To solve the symbolic code lock:
There are 4 total documents
The code is 6 symbols long

After finishing the basement:
V will still kick you out of his room. Others seemed to be fine with me going to other rooms

Locations and where their hints are. Tried to lay them out in order I found them

Stables - Safe - back corner of same room
Manager Office - Safe - In his quarters, in the basement
Luggage Room - Trunk - Symbol in room 11 on the ticket
Room 3 - Lockbox - Key under pillow in same room
Room 5 - lockbox - Given by Mantovani after confronting her about death
Room 15 - Papers - diagram found in locket outside coventry's room
Room 18 - Lockbox - code found in bath house locker 11
Wine Cellar - Number Lock - Found on notice board in servants hall, reversed date
Mens Dorm - Lockbox - Father Sinnott's sequence, found in room 8
Women's Dorm - Lockbox - uses 4 codes combined from basement, see basement section
Bath house - lockers - just locker 11, from key from The Trail

I believe this is available right from the start of the second day. It is interesting but fully self contained and you cannot ask or inform anyone about it

In the basement of the east tower you can find a hidden area. Inside you will find a ghost and remains. It directs you out and across the hall. Break your way into that room and get the remains there. Take them back to the first room for a cutscene and an achievement

Individual people and why I they were eliminated (or not) :
This will list out details about them as well as "facts about the culprit" you should learn on your own!
This WILL spoiler the culprit if you go through each person
Last warning, turn back if you want to solve it yourself
A. Hisham Wrong Religion
C. Joyce: Non-Magic/Staff
C. Mantovani: Knew Deane
C. O'Meara: Wrong feet, Knew Deane
C. Quinn: Knew Deane, Mourning
D. Hunter: Member of Staff
D. O Finn: Cannot Write
E. Toussaint: Wrong Religion
F. Callaghan: Wrong Religion, Wrong feet
H. Erickson: No Magic
I. Barbosa: No Magic
I. McLeod: Wrong feet
J. Blake: Mourning
L. Dupre: Mourning, Wrong religion
L . Sinnott: Arrived late
M . Skerritt: No Magic
O. D'arcy: No Magic
R. Callaghan: Knew Deane, Wrong Religion
S. Murphy: Cannot Write, Staff
S. Doyle: Member of Staff
S. Coventry: No reason
V. Lau: Mourning
V. Varley: Member of Staff
W. Blake: No reason