What I enjoyed about "Reese Comes Home" was the strong family bond between Reese, Malcolm and Dewey but also Lois' love for Reese. Her desire to put her life on hold and give up anything she had to to find Reese. She traveled around the world to bring him home and I thought that act she took was very poignant and very telling of her character. That no matter what your kids may put you through, for Lois, she loves her kids completely and will, literally, do anything to make sure they're safe.
The final scene when Malcolm and Dewey thought Reese was gone forever was so sad and the smile on their faces when they learned he wasn't was touching.
I thought that episode was the series at it's peak, in terms of character development and a flawless mix of comedy and drama.