Wonder Woman attends a party in Paris and meets Bruce Wayne (unaware he's Batman) when Princess Audrey of Kasnia is kidnapped by criminals. Wonder Woman rescues her and ends up as the somewhat flighty princess' protector and party-escort as she celebrates her last night before entering into an arranged marriage. Meanwhile, Batman deals with thieves who are after a control card controlling an orbital space platform. They escape with the card, but Batman captures one and interrogates him and connects him to Kasnia.
Wonder Woman meets Audrey's fiancée who is apparently . . . Vandal Savage (of "The Savage Time"). Savage claims he is Vandal Savage the 3rd, and the Nazi villain was his grandfather. Savage is working to perfect a Kasnian space program . Savage has a minion poison Audrey's father King Gustav, then his men go into space and take over an international space station, preparing it for use to launch a mass driver weapon. Wonder Woman pursues Savage and Audrey and Savage's minion Vox uses a built-in sonic weapon to deter her, while Audrey holds the marriage as planned.
Vandal Savage first appeared in Green Lantern vol. 1 #10 (Winter 1943). Originally he was a caveman named Vandar Adg who encountered a meteorite. Its radiation made him immortal and stopped his aging processes, but gave him no superhuman regenerative abilities or other abilities. Eventually taking the name "Vandal Savage," Savage ruled numerous civilizations either openly or behind the scenes. During World War II he clashed with the Golden Age Green Lantern and later the Justice Society, forming the first Injustice Society of the World. He has survived to the modern day and fought dozens of superheroes. Savage has a vast knowledge of sorcery and technology and uses either or both depending on the circumstances. This is his first appearance with clear knowledge of who and what he is in the WB animated universe.
Believe it or not, Colonel Vox is actually an established DC character. He appeared in one issue of one comic - Metal Men #51 (cover date April-May 1977). He hasn't appeared since, except here. Needless to say, this is his first appearance in the WB animated universe.