Hilary Marsden is a disciple and accomplice of domineering serial killer and con man Bernard Fremont. She joined Fremont in his criminal enterprise after being released for crimes committed with Nicole Wallace in Thailand. Her parents reported her missing in Hong Kong, and Hilary even changed her looks to look like Nicole as Fremont had made her present herself.
Hilary joined Fremont in his pack of con artists and robbers, including her reunited sister Mala, with Hilary's role being a scout posing as a real estate agent to find high-end homes to strip clean and rob of all valuables salvageable and deemed fitting Fremont's pawning. The victims would be drugged and even killed, and when Fremont killed a biographer, Wesley Banyon, who would've tarnished his name, Hilary and the other conspirators decapitated him and threw his body into the river.
Hilary and the accomplices started making mistakes when she overdosed Russ and Monica Corbet on heroin while robbing them, but only Russ died. Marcel Costas also left Banyon's head in the freezer at his stripped apartment, so Hilary while as Fremont ordered Mala to strangle Costas to death while drugged, just before the remaining gang celebrated with drinks.
When Hilary's identity was found out, the detectives tried to make Hilary turn on Fremont. But since she as so imprinted by Fremont's influence, she wasn't shaken. So when Fremont was tricked into believing it happened, while also being read Banyon's manuscript, that was enough for a confession. Hilary, Fremont, and accomplice Sammie all pleaded not guilty, and Mala posted their bail while cameras flashed at them. However, Freemont and Mala were walking down the court steps, Nicole bumped into Fremont, poisoning him with a syringe filled with an unknown substance, to Mala's horror. Hilary's status is left unknown. (CI: "Slither")