He was portrayed by John Malkovich, who also portrayed Dave/Dr. Octavius Brine in The Penguins of Madagascar, Mitch Leary in In the Line of Fire, Cyrus Grissom in Con Air, Humma Kavula in Hitch-hiker's Guide to the Galaxy, Tom Ripley in Ripley's Game, Pascal Sauvage in Johnny English, Teddy Deserve in Knockaround Guys and Vicomte Sébastien de Valmont in Dangerous Liaisons.
According to that film's storyline, Turnbull is a former general officer in the Confederate Army, who (after the Battle of Gettysburg) intentionally targets civilians - hospitals, churches, schools - in an attempt to turn the Union's people against their government (in effect, becoming a proto-terrorist). During the final years of the War, he orders Jonah Hex to burn down a hospital, but Hex refuses, and is forced to kill Turnbull's son, Jeb. Hex later turns Turnbull and his men in to the Union military. Swearing vengeance, Turnbull ties up Hex outside his house and forces him to watch as his house is burned down with Hex's wife and son inside. He then brands Hex's face with the initials "QT" and leaves him to die. Hex later removes the initials by searing his face with a heated tomahawk. Turnbull fakes his death and lies low for several years, resurfacing to mastermind a terrorist attack on the United States during its centennial celebrations. He steals a "superweapon" designed by Eli Whitney, and plans to use it, mounted on an ironclad, to level Washington, D.C.. He is killed when Hex traps him aboard the ship and detonates the magazine, exploding the ship.