Here is the full list of all 18 Blackwell Epiphany achievements.
Complete the story
Free yourself
Learn a long kept secret
Blow on everyone you can find
Two becomes one
Make a leap without falling once
Reunite a family
Keep clam and keep cool
She has plenty of time...
Gain access to an online game
Save your first ghost
Solve a puzzle together
Finish the game in commentary mode (from the first screen till the last)
Find a secret room
The hows and whys of Joey
Try to lie your way out of it
Create no more than 450 footprints
Somebody's got to do it...