Sydney is a supporting antagonist (later anti-hero) of the 1964 James Bond film Goldfinger. She is a member of the Flying Circus (led by Pussy Galore) who was under the employ of Auric Goldfinger of Auric Enterprises.
She was portrayed by Tricia Muller.
Being under the employ of Goldfinger, Sydney was tasked to spread the Delta 9 nerve gas across the area of Fort Knox that will kill 60,000 people in order for Goldfinger to lead his task force (led by Oddjob and Kisch) to smuggle a nuclear bomb (created by Mr. Ling) into the vault. Such an action would make the gold radioactive and useless for 58 years, and that the value of Goldfinger's gold will increase many times, thus making Goldfinger the richest man in the world.
Upon the arrival of James Bond (as he was invited to personally witness the preparations of the operation after being captured by Goldfinger), Denise was seen transporting Bond in Goldfinger's plane. When Bond goes to change his clothes, Galore asks Sydney to have their servant Mei-Lei to spy on him. After landing their plane in Kentucky, Sydney and the other pilots were assured by Galore that they will get their assignments tomorrow night. She then dismisses them for the day before transporting Bond to Goldfinger's ranch, where Bond learns of Goldfinger's plot.
With that in mind, Bond seduced Galore into foiling Goldfinger's plan, so she had Sydney and the other pilots to replace the nerve gas with a harmless one while alerting the U.S. government about Goldfinger's plan. It is unknown what happened to Sydney following the deaths of Goldfinger and his men.