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