Lyle Peck is a museum tour guide who plotted to steal a valuable moon rock from the museum but couldn't get past security the old fashioned way so he planted it in an aquarium set in the giftshop and marked the box for his accomplice, Brian Lemmon, to purchase. Problem is, Julie Teeger, bought the box set. He then trailed Julie to her home and posed as a water meter reader in order to find and retrieve the rock. When that failed, Brian snuck in during the night only to be stabbed by Natalie Teeger. When Julie took her aquarium to her school science fair, Lyle created a diversion by starting a fire and stole the moon rock from the aquarium while sweeping up the fish as well. Monk spotted Lyle and chased him to another wing of the school where Lyle tripped on a flight of stair. He was then arrested by Captain Stottlemeyer.