He was apparently killed by the Darach during her "Warrior" sacrifices. A plaque on his desk at school featured the "Cadet Honor Code" from The U.S. Military Academy at West Point - "A cadet will not lie, cheat, steal, or tolerate those who do."
We learned that Mr. Harris gave a woman he met in a bar information about how to commit arson and get away with it. He believes this mysterious woman ultimately used that information to burn down Derek Hale's home. The woman is later revealed to be Kate Argent.
He quotes Einstein in class pointing out the unlimited nature of the universe and human stupidity. He has the students change partners throughout an experiment to make rock candy. This gives Erica and Isaac a chance to test Lydia with kanima venom. (read more...)
He later gives Scott, Stiles, Jackson, Allison, Erica, and Matt detention after Jackson and Scott have a fight in the locker room. He follows when Jackson leaves the library and heads to the bathroom due to nausea. He then leaves in a hurry and drives away in a VW Jetta with an Einstein bumper sticker. (read more...)
Harris is brought in for questioning. Tire tracks matching his car were found at the trailer in the woods and an eyewitness saw it, and the Einstein bumper sticker, at the hospital on the night of the murder. (read more...)
After handling lunchtime detention, Adrian Harris is kidnapped and tied to a tree. He begs for his life, telling the killer: “I did what you asked. I did everything. They’re going to figure this out and they’re going to find you. You still need me.” The killer then twists the stick, tightening the garrote around Harris neck. (read more...)
A photo of Mr. Harris is seen on Sheriff Stilinski's police board when he tries to connect some deaths to supernatural occurrences. (read more...)
- “However, as happens every year, one of you will inexplicably fail to put your name on the cover, and I will be left yet again questioning my decision to ever become a teacher.” — Harris to a class before a test (Lunatic).