Mr. Arlert

 was the father of Armin Arlert.

Personality
Mr. Arlert appeared to be a very courageous man, willing to risk his own life in order to escape beyond the Walls. The fact that he was able to design a hot air balloon that would carry him and his wife beyond the Walls indicates that he was remarkably intelligent man.

History
Mr. Smith and his wife were both killed by Military Police Brigade member Djel Sannes for attempting to escape the Walls.