Agatha Christie - Hercule Poirot: The First Cases

Story-related; cannot be missed.

Here is a walkthrough of the prologue, including everything needed for achievements.

Garden
Talk to Elizabeth
Look at the muddy footprints right by her, then follow the tutorial
Head down to the gazebo just below you and look at the plaque inside
Go to the right of the gazebo and look at the overgrown grass
Look at the waterlogged grass above the gazebo
Follow the tutorial to learn how to make deductions, then talk to Elizabeth

Mind Map
"Intruder didn't use the lawn" + "Intruder didn't use the path"

Garden
Just to the left of Elizabeth is an interaction point for the open window on the second floor of the house. Interact with it
Look at the front door of the house
Look at the trellis to the right of the door
Look at the flowerbed to the right of the trellis
Look at the bench to the right of the flowerbed
Look at the ladder to the right of the bench
Look at the side door to the right of the ladder

Mind Map
"Open window" + Wooden ladder"
"Side door" + "Front door"
"No forced entry" + "No scaled access"
"No unlawful entry to the house" + "No unlawful access through the garden"
It wasn’t a burglary (15G) unlocks

Garden
Talk to Elizabeth twice
Interact with the front door of the house to enter

Main Hall First Floor
Talk to Cassandra, then follow the tutorial
Look at the crate in the bottom right corner of the room
Look at the telephone on the table in the back right corner
Look at the portrait on the back wall
Look at the books on the shelf on the leftwall
Interact with the Lounge door on the left side of the left wall
Interact with the Kitchen door on the right side of the left wall
Look at the coat on the back left well
Talk to Cassandra again
Go up the stairs

Main Hall Second Floor
Interact with the Bathroom door on the far right side
Look at the spot on the wall where the obvious missing painting was
Enter the Bedroom door on the left

Bedroom
Talk to Angeline
Look at the rag on the desk right by where you entered
Look at the fireplace
Look at the jewelry box on the table at the right wall
Look at the fireplace poker on the floor
Look at the photograph on the vanity in the back of the room
Look at the broken glass on the floor
Look at the open window
Look at the dust spot on the night stand "behind" the bed

Mind Map - Cassandra
"Strange symbol" + "Quote on a plaque"
"Missing painting" + "Auction crate"

Mind Map - Crime Scene
"Unprotected" + "Broken glass"
"Open window" + "Abandoned poker"

Bedroom
Talk to Angeline
Angeline Van den Bosch (15G) unlocks
Exit the bedroom
Go downstairs
Go back out the front door

Garden
Talk to Elizabeth

Mind Map - Cassandra
"Elizabeth confirmed spare key" + "Interest in Shakespeare"

Garden
Talk to Elizabeth
Go inside
Go upstairs

Main Hall Second Floor
Look at the books next to the Bathroom door
Go downstairs

Main Hall First Floor
Interact with the door on the left on the left side of the room to enter the Lounge

Lounge
Talk to Florette
Look at the note at the left side window
Luc Piette (15G) unlocks
Look at the poker stand next to the fireplace
Look at the pastries in the right corner
Look at the wet package next to the pastries
Look at the personalized handkerchief
Look at the letter on the little table next to Florette
Look at the collection slip on top of the barrels in the corner
Look at the single wine bottle
Fine-toothed comb (25G) unlocks
Leave back to the Main Hall
Exit back to the Garden

Mind Map - Cassandra
"Final demand" + "Telephone"
"Financial responsibilities ignored" + "Selling heirlooms"
"Cassandra is desperate for money" + "Valuables are insured"

Mind Map - Crime Scene
"Personalized handkerchief" + "Cleaning rag"

Garden
Talk to Elizabeth

Mind Map - Crime Scene
"Angeline removed soot stain" + "Fallen soot"

Mind Map - Florette
"Abandoned poker" + "Poker stand"
"Collection slip" + "Address label"
"Parcel was collected from tailors" + "Florette was dawdling"
"Florette was running an errand" + "Cassandra watched Florette"
"Florette had no opportunity" + "Theft fits Cassandra's insurance scam"

Garden
Talk to Elizabeth

Map Map - Elizabeth
"Note from Luc" + "Bench carving"
"Elizabeth and Luc are courting" + "Gold band"
"Elizabeth and Luc are betrothed" + "Formal suit"

Garden
Talk to Elizabeth
Elizabeth Padget (15G) unlocks
Go inside the house
Enter the Lounge

Lounge
Talk to Florette
Exit to Main Hall

Main Hall First Floor
Talk to Cassandra - Understanding, Empathetic, Sympathetic
Go upstairs
Enter the Bedroom

Bedroom
Talk to Angeline
Look at the fireplace

Mind Map - Crime Scene
"Someone forced the window open" + "Angeline stashed her keepsakes"
Little grey cells (15G) unlocks

Bedroom
Exit the bedroom
Go downstairs
Enter the Lounge

Mind Map - Florette
"Cassandra became aggressive" + "Cassandra previously mistreated Florette"
"Florette is mistreated" + "Florette was scapegoated"

Lounge
Talk to Florette
Florette Duval (15G) unlocks
Exit the Lounge
Exit the house back to the Garden

Garden
Talk to Elizabeth
The Bracelet (50G) unlocks after the cutscenes