Four walks down the hallway toward the stairway that leads outside.
Four gets on the train and sets off of the Abnegation sector. To go to Marcus's house.
Once he gets to the Abnegation sector he still remembers how to get to his old house.
When Four get to the house he knocks on the door no one answers so Four takes the hidden key from under the doormat and opens the door. Then he walks into the house and he sees Marcus.
Marcus was mad that Four came back and he said that Four was "no longer welcome in this house." But Four did not care and told Marcus about the attack plans on Abnegation that Max and Jeanine were planning. Marcus did not believe what Four was saying.
Four was upset that his father didn't believe him. So he walked away and went back home.