Gene Marshall is a character in DEXTER as well as Dexter Early Cuts. He was a fire inspector and a serial arsonist. He is one of Dexter's earliest victims, dying in 2002 (1 year after his first blood slide victim, Alex Timmons).
Gene is a tall man with light brown hair, he wears a brown business suit.
Gene is a very chaotic person. Despite the fact that he built up a million dollar industry, he set his own apartment complex ablaze and stood there, willingly in charge of himself as he watched innocents burn. Even after being considered mentally unstable, he showed no remorse and instead lied to Dexter saying he couldn't help himself...something simply to hide the Dark Passenger within him...much like Lila West. He also has an amazing survival rate, being alive after his neck was slit and returning to try and kill Dexter...which unfortunately for him, fails.
Whether or not his Showtimes series had the same motivation for burning down the apartment complex is unclear, as they did not have exactly the same personality, as the Showtimes series Gene did not have the same survival rate as the Early Cuts Gene.
Dexter's description in Early Cuts.
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 6 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, although in the TV series storyline, Deb said he inherited it from his father, Harry Morgan.
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 bunch of candles around Gene. Before his death Gene asked Dexter if he knew how it felt to see anyone 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.. 
- Although he is killed prior to Dexter taking blood slides (according to Early Cuts), he still has a blood slide in Dexter's collection.
- 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 2 and the Phantom Arsonist (Joe Jensen) in Season 7.