You were mad. Everyone was mad. After finding out Marlon traded Sophie and Minny, and also killed Brody, Clementine locked him in the basement.

Louis was the only one that went down to talk to him or give him food and it made Marlon feel even worse, sure, it was good SOMEONE talked with him, but the guilt was eating him alive. The fact that no one else could look at him was killing him, and he really really regreted his actions.

When he heard the basement door open and close he didnt even move because he expected it to be Louis again. Then he saw your silhouette appear "Oh, shit, hi.." He stood up quickly.