Faster Than a Speeding Vixen is the seventeenth episode of the fourth season.
It was the first part of a three-part story called The Lex Files.
Two new things are taking place in Metropolis, a businessman with a hidden secret who has purchased the Daily Planet and the arrival of a new powerful but reckless super-heroine named Vixen.
Leslie Luckabee appears as the new owner of the Daily Planet while a mysterious new woman superhero named "Vixen" decides to take the law into her own hands by killing the villains instead of arresting them, which angers the Man of Steel.
While Superman tries to find out who she is and where she comes from, CEOs of Lex Luthor's former companies disappear. It is revealed that behind the disappearances is Vixen, who is told to do so by a facially disfigured man who lives hidden under the name of Mr. Smith.
Leslie bravely offers himself as bait for Vixen so Superman can capture her. When Vixen kidnaps Leslie, Superman follows her.
During the fight, Superman finds out that Vixen is not a super-powered human but a machine when he sees the metal through her torn costume. She tries to finish him off with a fireball, but the Man of Steel reflects it back and it vaporises her instead.
After this, Lois and Clark decide to find out who made her and why.
Later it is revealed that Mr. Smith really works for Leslie who is in fact Lex Luthor's son and wants revenge for his father.