Derek Philby is a murderer featured in Season 2. He was a science teacher at Ashton Preparatory High School who was having an affair with English teacher Beth Landow. Beth demanded that Derek leave his wife or she'd bring their affair to life. Derek then suggested he'd do that as soon as the SAT's were done. The next day Derek requested her to meet him up on the bell tower where he strangled her, then placed her on the minute hand of the bell tower, so that while he was overseeing his students take the SAT's, the minute hand went down far enough for Beth's body to slide down and land on top of his car. He was approached by Iverson, the school groundskeeper, claiming he saw Derek kill Beth and requested $10,000 as hush money. That night, Derek snuck into Iverson's home where he punctured a hole in the gasline near the fireplace and planted a matchbook near his bedroom door with a match ready to swipe it. The trap was a success as Iverson was blown up in his house. After learning that there may have been evidence suggesting foul play, Derek snuck back in the bell tower and found Beth's glasses inside the bell tower, but upon leaving the tower, he was surrounded by Adrian Monk and the SFPD. Adrian then pointed out that the glassed were at the top of the Bell Tower, not inside. Derek was then arrested for murder.