Agatha Christie - Hercule Poirot: The First Cases

Story-related; cannot be missed.

Here is a walkthrough of the chapter, including everything needed for achievements. Note that there are some highly missable achievements/items in this chapter.

Major's Study
Talk to Archibald
Look at the Major's body
Look at the damp floor
Look at the burned carpet
Look at the safe in the corner of the room
Look at the dent in the plaster up on the wall between the two mounted animals
Look at the letter on the chair
Look at the wallet on the floor
Look at the ice bucket in the left corner
Look at the window

Mind Map - What Happened Prior
"Sum of money" + "Jewelry box"
"Second floor window" + "Valuables not taken"
"Damp floor" + "Remaining ice cubes"
"Bucket was overturned" + "Unrepaired"

Major's Study
Interact with the door to try to leave the room

Mind Map - What Happened Prior
"Evidence of a fight" + "Logical entry point"

Major's Study
Talk to Archibald
Look at the Major's jacket on the coatrack
Look at the ashtray
Look at the towel
Look at the matchbox
Look at the desk
Look at the fireplace poker stand
Look at the fireplace

Mind Map - Who May Be Responsible
"Half-smoked cigar" + "Burn mark"
"Missing knife" + "Single stab wound"
"Very tidy" + "Bucket was overturned"
"Crime scene was compromised" + "Clean"
"Moldy logs" + "Ring of dust"

Major's Study
Talk to Archibald

Mind Map - Who May Be Responsible
"Unused fireplace" + "Empty matchbox"
"No fire source" + "Evidence of smoking"
Truth from within (15G) unlocks
"Someone lit the Major's cigar" + "Killer's entry to the room"
"Major knew his killer" + " Crime scene was compromised"

Major's Study
Talk to Archibald and he'll take you to the Major's Bedroom

Major's Bedroom (this is the only time you will be in this room)
Look at the letter
Look at the note on the fireplace
Look at the dresser drawer
Look at the window

Mind Map - Who's in the House
"Margaux protective" + "Close to Cassandra"
"Mention of helping family" + "Ernesto supports"
"Hugo's positive work" + "Gedeon is a supporter"

Major's Bedroom
Talk to Archibald

Mind Map - Who's in the House
"Cassandra has multiple admirers" + "Love for Cassandra"
"Multiple guests threatened..." + "Killer may still be in the house"

Major's Bedroom
Talk to Archibald
The Major (25G) unlocks