|First Appearance||Falling Skies, Chapter 3|
|Last Appearance||Falling Skies, Chapter 5|
|Occupation||Maths Professor (Pre-Invasion)|
|Cause of Death||Killed by a Beamer.|
|“||You should read your own history books, Thomas. Then you would know that, for all men, there will come a day when they go to war. This is whether they fight for a throne, or a woman, or the skies above.||”|
— Alex to Tom.
Alexander Vlensa was a math professor, and as described by others a "conspiracy nut" who obsessed over war and weaponry.
Alex was a math professor at Boston University at the same time Tom Mason taught there. When Tom Mason joined the 2nd Mass he suggested that they attempt to find Alex Vlensa's weapons cache, but were initially unsuccessful until they got a lead 6 months later. It is revealed that Alex first traded guns to the antique toy shop group for some food.
Later when Tom and his squad come to Alex looking for guns he gives them his stash but saves a rocket launcher for himself. Then when an attack squad of Skitters and Mechs arrives Alex and Reed attack them, Alexander and Reed hold their position, killing many Mechs and Skitters. When Alexander asks Reed a question, he turns around to see Reed being killed by a Skitter, then soon after the aliens retreat to Alexander's confusing, however when he looks up he understand, and a Beamer drops a bomb right over Alexander, killing him.