Two twins, Daniel and Sandra, are separated when very young as their parents split up without any contact for nearly 20 years. When they meet by chance on their 20th birthday this drama series starts, and the first main storyline is whether or not they will get to know that they are related. Their two families (of different world, hence the title) are upper and middle class. Daniel's brother Mikael elopes with Anna to live as outcasts, as Anna's mother blames Daniel and Mikael for the murder of her husband. Andreas is revealed as the real killer, but doesn't succeed in proving to the court that the death was an accident, so Andreas has to spend time in prison. His girlfriend is Daniel's and Mikael's sister Stina, who is torn between her family and boyfriend.