Here is the full list of all 27 Intruders: Hide and Seek achievements.
Complete the story.
Get all the documents.
Get all the collectibles.
Check out all the computer documents.
Complete chapter 1.
Complete chapter 2.
Complete chapter 3.
Complete chapter 4.
Complete chapter 5.
Complete chapter 6.
Complete chapter 7.
Complete chapter 8.
Get half of the documents.
Get half of the collectibles.
Escape 3 times from an enemy.
Use 5 hiding places.
Close 5 doors.
Walk about crouching 100 yards.
Get a document.
Get a collectible.
Escape from an enemy once.
Successfully complete the panic mini-game once.
Fail the panic mini-game once.
Use a duct.
Use a hiding place.
Close a door.
Make Irene remind you about the mission once.