In the far furture, a strange alien race named the 'Hondon' have come down to earth to claim more land. The only way to do that is to enslave all the humans to work for them. Much like the English and Indians. One Hondon fell in love with an Earth female and they mated. The Hondon found out about this and killed the father. The mother Luciel managed to escape, and gave birth to Sydney and Max.
Skip to a few years later, we see them fourteen and hunting the Flame Pups that the Hondons managed to bring. They don't know of their mothers past -just that she lived as a slave and managed to escape- so everything is fine.
They come back and see their mother dead with traces of the Hondon. They set out to take revenge and slowly learn of their mother's and the Earth's past. And just who killed their mother.