Number of achievements: 46
Number of missable achievements: at least 6 (A rude awakening, A curious phrase, Johan Kristiansen, A perilous journey, Perkins, A true performance)
Minimum Playthroughs: 1, chapter select available
Free-Roam After Story: No
Does difficulty affect achievements?: No

All achievements are fairly easy to obtain. The missable achievements (one in chapter 5, two in chapter 6, two in chapter 7, one in chapter 9) are quite easy to unlock if you're thorough with your inspecting. However if you miss them you can use chapter select to reply a chapter.

Achievements are presented in chronological order although due to the nature of the game it's possible to unlock them in a slightly different order depending on your decisions like which location visit first or which character talk to first.

*Note: It's possible more achievements are actually missable. These were the ones I found during my playthroughs.

Marc Allard
Uncover a secret about Marc


Talk to Marc and ask him about drinking alcohol at work.


Little ideas
Solve 5 match puzzles


Solve five "match" puzzles (select one or two items from the list to continue dialogue)


The Ship
Complete the Prologue


Complete the prologue.

Seeking the truth
Ask 25 questions


Select 25 dialogue options


An old friend
Solve all of Zakariya's artwork challenges


Solve Zakariya's paintings riddle:

1. Monsieur Kristiansen - Narcissus - Vain
   
2. Mademoiselle Warbeck - Joan of Arc - Underdog
   
3. Madame Betty Allen - The Wild Horse - Plays down her personality for British society
   
4. Mademoiselle Farquhar - The Worker Bee - Hard Worker
   
5. Monsieur Ailsworth - The Good Samaritan - Passionate about charity work
   
6. Bishop Mountjoy - Judgement Day - Judges people harshly
   
7. Mademoiselle Court-Smyth - The mechanical orrery - Centre of attention

The Gala
Complete Chapter 1


Complete Chapter 1

A curious gathering
Find all evidence in the museum


Find all 10 clues in the museum:

1. Toppled vase
   
2. Painting hook on wall
   
3. Painting hook on floor
   
4. Skylight (on the floor)
   
5. Heating vent
   
6. Broken glass found on the floor
   
7. Opera glasses
   
8. Skylight (use Opera glasses)
   
9. Door to restoration room
   
10. Door to the main hall

Little grey cells
Make 10 deductions


Make 10 successful connections in mind maps


Arthur Hastings
Uncover a secret about Hastings


Automatically after talking with all the suspects


Impossible is possible
Solve 3 mind maps


Complete three mind maps


The Missing Magdalene
Complete Chapter 2


Complete Chapter 2

Everything matters
Perform 10 analyses


Analyses are inspections of items with points of interest


DI Hardwicke
Uncover a secret about David


Talk to DI Hardwicke in the Museum exhibit


An expert mediator
Diffuse some arguments


This should unlock after talking to Horace about Mortimer's heart attack


Order and method
Use 10 items


Self explanatory, it will unlock naturally


Betty Allen
Uncover a secret about Betty


Give the ring found in the heat vent back to Betty.


The Investigation Begins
Complete Chapter 3


Complete Chapter 3

Irene Court-Smyth
Uncover a secret about Irene


Discover that Irene was selling forgeries by solving her mind map


Ms. Camilla B. Culsham
Uncover a secret about Camilla


Talk to Camilla to learn about Irene's guests


An odd series of events
Unravel Culsham's chain of events


Talk to Hastings about events described by Camilla


The Apartment
Complete Chapter 4


Complete Chapter 4

Nathaniel Dryden
Uncover a secret about Nathaniel


When talking to Nathaniel threaten to take the story about Betty elsewhere



A rude awakening
Annoy a politician


Talk to Mortimer about Irene's death


Bartholomew
Find a missing cat


Figure out that the cat is in the confessional and use a jug of cream to lure it out


The Scheme
Complete Chapter 5


Complete Chapter 5

Zakariya Demir
Uncover a secret about Zakariya


Talk to Zakariya about the weekend at the van den Bosh mansion (previous game)


Anastasia Babanin
Uncover a secret about Anastasia


Talk to Nathaniel about Florence's visitors


Well-acquainted
Meet all characters in the game


After introducing yourself to Nathaniel (not during the first dialogue with him)


Truth from within
Crack 3 safes


Open three safes in the game.


A curious phrase
Solve the mystery of the note


Decrypt the Strange note from Jewellery box, use it on Notepad in Johan's apartment, decode the phrase using Norwegian dictionary



Johan Kristiansen
Uncover a secret about Johan


After finding love letter from Irene to Johan in his safe



The Suspects
Complete Chapter 6


Complete Chapter 6

Evelyn Lakshmi Warbeck
Uncover a secret about Evelyn


Talk to Horace at the beginning of the chapter.


A perilous journey
Inspect all stations of the cross


Missable. There are 13 paintings and a stand with missing painting depicting Stations of the Cross in the church. Inspect them all.


Horace Mountjoy
Uncover a secret about Horace


Find Horace's stash with paintings.


Perkins
Visit a lonely dog


Missable. When you're in Irene's apartment leave to the hall, go downstairs and interact with the door to Ms Culsham's apartment.


The Secrets
Complete Chapter 7


Complete Chapter 7.

Mortimer Ailsworth
Uncover a secret about Mortimer


Inspect drawer in Mortimer's office once he's gone.


A peculiar fellow
Unravel Mortimer's movements


Solve the mind map to figure out what Mortimer was doing when you knocked the door.


Well-travelled
Visit all locations in the game


Automatically after entering the dark room.


The Investigation Starts Anew
Complete Chapter 8


Complete Chapter 8.


Florence Farquhar
Uncover a secret about Florence


Talk to Hastings after resolving the light issue in the dark room.
Note. This unlocks after achievement for completing this chapter, but before starting the next one.

A true performance
Deliver your findings, flawlessly


Don't make any mistake during the denouement.

• Evelyn - Evidence tampering
  
• Florence - Aided forgery creation
  
• Horace - Theft and embezzlement - "I can assure you (...) Business Partners"
  
• Mortimer - Insurance fraud - "And you wish to present yourself as a sick man?"
  
• Johan - Theft
  
• Talk to the rest of the guests
  
• Inspect three paintings

The Penitent Magdalene
Deliver your findings


Automatic during the final speech.


A treasured heirloom
Work out what happened to the cigarette case


Automatic during conversation with Anastasia.


The Denouement
Complete Chapter 9


Complete Chapter 9.

Thank you to NS Plover for pointing out missing achievements.