Ten (voiced by Olivia d’Abo) aka Melanie Walker is the youngest member of the Royal Flush Gang, a family of criminals including "King", "Queen" - Ten's parents -, her brother "Jack" and "Ace", an android. As such, they are recurring foes in the Batman-Universe, still active in "Batman Beyond" (also known as “Batman of the Future”) where Terry, a teenager, becomes a new batman with the old one as his councilor and fatherly friend.
Melanie Walker
Ten
"Ten" and "Batman" first meet as Melanie and Terry, students of the same high school. From their first encounter, there is a strong erotic sizzling between them - they even have a couple of dates while "Batman" is trying to capture the whole Royal Flush Gang, including Ten, of course, so the lovebirds fight each other several times while in disguise.
During the climactic battle, Batman is able to take out the whole criminal family one by one. He saves Ten from a deadly fall out of a skyscraper and eventually realizes that the unmasked girl he holds in his arms is Melanie, his almost-girlfriend. Although both don't seem too happy with the outcome, Ten is handed over to the police and shares her family's fate: all gang members are unmasked, put in futuristic manacles and secured in a prison van. A very sad and somehow ashamed "Ten" gives Terry a last melancholic look before being taken away. During the episode, it has already become clear that she is not convinced of what her family does and wants to find a way out of crime, so she should be classified as remorseful or even redeemed - although her perspective clearly includes some jail time as punishment for her crimes.
After "Ten" has been put in the prison van, the older (and original) Batman tries to cheer up his sad apprentice by proposing to tell him about a woman he once knew called Selina Kyle (a hint to Catwoman and her "on-the-cuff"-romance with Batman).
"Ten" is an athletic young woman with long blond hair (hidden under her mask while "on duty"). Her character is different from her family: she doesn't seem to enjoy violence and crime, but is rather melancholic and unhappy with her life.
Ten is a recurring character of Batman Beyond, first a criminal, later redeemed. She appears in the following episodes: “Dead Man’s Hand” (1.8; first appearance and arrest); “Once Burned” (2.7; Ten is back from jail, now redeemed); “King’s Ransom” (3.1).
For more detailed information, see http://batman.wikia.com/wiki/Melanie_Walker
