Gene is a tall man with light brown hair. He wears a brown business suit.
Marshall set his own apartment complex ablaze, not caring that seven innocent lives were lost. He was judged mentally unstable and showed no remorse, telling Dexter that he couldn't help himself.
"Gene Marshall...real-estate mobile, millionaire...and arsonist. Set fire to one of his own apartment complexes. Didn't matter that his insurance policy had expired or that a dozen residents were still inside. Marshall lost six million dollars and seven innocent people lost their lives."
Marshall was a real-estate developer and millionaire who set one of his own apartment complexes on fire, killing seven people. His psychiatrist deemed him mentally unfit to stand trial (the fact that Marshall hadn't paid the insurance and lost millions of dollars because of the fire probably helped). After three months in a psychiatric institution, Marshall was released and went back to his usual life of luxury. Dexter later restrained him in plastic and slit his throat with a pocket knife. When he was about to cut up the body, Deb called, having just received her driver's license and wanted to take him out for a drive to celebrate her birthday. In a hurry, Dexter put Marshall's body in the trunk of his own car and headed to the apartment complex Marshall had burned. Unfortunately, Marshall didn't die, but grabbed the knife and attempted to slash Dexter when the trunk was opened. Dexter knocked him unconscious with a flashlight and finished him off by driving over his head with the car. Dexter then attempted to dispose of the body parts by setting them on fire with gasoline, only to have the fluid explode. In the Early Cuts storyline, Dexter now purchased his boat, Slice of Life, to get a better way to dispose of his victims.
When the Ice truck killer had brought back from ocean Valerie Castillo, Dexter's last victim, which resulted in police investigation, Dexter decided to eliminate any evidence that might implicate him. He threw his instruments in ocean and was about to do the same to his slides. Before doing that Dexter went through his collection of blood slides and remembered some of his victims. Gene was second victim that Dexter remembered. Like most of Dexter's victims Gene was wrapped in plastic wrap and had scar over his right cheek. Dexter had also placed candles around Gene. Before his death, Gene asked Dexter if he knew how it felt to see someone burn alive.
Unlike Cindy and Alex, there is no direct inconsistency between his kills in Early Cuts or the Showtime series so all of his victims can be considered canon as a whole. Gene was noticeably prolific as a murderer, being responsible for the deaths of seven people; not only does he appear to be one of the most prolific of all the murderers to be killed by Dexter in the Showtime Series, he may have actually been the most prolific prior to the death of the Ice Truck Killer at Dexter's hands.. 
- Herb Watson (73)
- Jacob Williams (31)
- Harold Tress (44)
- Bob Mority (27)
- Kim Yancy (29)
- Vince Colbert (33)
- Craig Johnson (40)
- Although he is killed prior to Dexter taking blood slides (according to Early Cuts), he still has a blood slide in Dexter's collection in the TV series.
- He shares his last name with serial killer Travis Marshall, however no other relation exists between them.
- Gene Marshall is an arsonist (uses fires as main killing method) just as Lila West in Season Two and the Phantom Arsonist (Joe Jensen) in Season Season