You need to decide what Corliss will do from the second day onwards. 
She can choose to clean the house or go outside to buy groceries and the like.
Each action will give you a "hint", which will be used to determine the past story that Corliss will see within her dream.
There are 5 routes in total (2 Nathan, 2 Ethan, and 1 True route).
If you can't enter any specific room at the fourth day, you will be automatically directed to the bad ending.
The true route will have a bad and two other endings, which means there are 8 endings in this game (2 Bad).
Corliss's feeling will gradually awake within each of the routes on Nathan's and Ethan's path.
You need to clear all Nathan- and Ethan-related routes, and restart the game from the prologue to unlock the hidden true route.