Stu "Cobb" Cobbler was an unpopular Neptune High student who read gun magazines during class and dealt drugs. He also had a crush on Gia Goodman. Gia and her friends wanted to hit him up for drugs, but he managed to worm his way onto their party boat trip. That night, Susan Knight was found unconscious and her breathing was starting to waver. Everyone panicked. To calm everyone down, he told them that Susan would just sleep it out and that he'd seen it a hundred times. The next morning, however, Susan was dead. Stu suggested weighing her down with an anchor and throwing her body overboard. Gia, Luke Haldeman, and Carrie Bishop did so; Stu took a photo of them in the act and used it to them to blackmail the group for years afterward.
Carrie started to feel extremely guilty, even going so far as to include themes from that night in her new (final) album, Confessional. Stu decided that it was time to shut her up and blackmailed Gia and Luke into helping him murder Carrie. Gia lures Logan Echolls to the scene, making him the primary suspect.
Stu finds out that Veronica Mars had bugged Gia's apartment and manages to use the bug to listen in on Veronica and Gia. He then murders Gia when she approaches the window. After missing Veronica by inches, he goes after her in Gia's apartment. Veronica manages to incapacitate him with her Stun Gun and Pepper Spray and run out of the apartment, but the exits were locked. Stu comes after her, but she manages to knock him unconscious with a golf club. He is then arrested by Dan Lamb.