Who Is "The Professor" on The Perfectionists? Breaking Down the Most Likely Suspects

Why She's the Killer:

• Let's be real, Mona has always been a little sketchy. She was the first "A" on Pretty Little Liars, after all.
• She also has some deep ties to the college and their secret surveillance of the students. Whether it was intentional or not, maybe she helps the professor facilitate Nolan's murder.

Why She's Not the Killer:

• Though Mona is a bit unhinged at times, she immediately becomes hell-bent on decoding the school's surveillance software so that she can find Nolan's killer.
• She is part of the group being surveilled by the professor.