Dennis Gogolack is a childhood friend of Shawn and Gus's who attended grade school with them. When the two visit him to consult him on a case, Dennis is surprised to see them again after so long and brings them to a hidden room that contains his nerdy interests and memorabilia. He doesn't mind letting his nerd out on Shawn and Gus since they knew him way back when, but he wants to keep it a secret from his wife Molly because she has made herself quite clear that she's only attracted to macho types.
Later, Shawn and Gus visit Dennis again and convince him to hack Lassiter's computer to get info before he does. Dennis somehow remotely hacks into Lassiter's computer with ease, as he apparently hacked into the National Weather Service's network a few years ago. The drive contains legal documents that are related to a textile company that was recently responsible for a major chemical spill that Kessler believes to be intentional.
Dennis later appears at the warehouse where Shawn and Gus are being held captive, pretending to be a delivery guy. He pulls out nunchucks and tries to disarm the guards in order to save his friends but is taken down by Lassiter and Juliet when they suspect him of being a criminal as well.
By the end of the episode, Dennis is seen hanging out with Shawn, Gus, and Kessler in his secret room. Molly ends up discovering his secret room and how he is a nerd, but fortunately for Dennis she reveals that she is a closet "nerdette" herself.