As a demon and a fallen angel battle for his soul, a tormented serial killer is stalked by the ghosts of his past victims and hunted by detectives searching for his latest prey.
This is the backstory of Hana and Joon Seung, characters in the series "MARS" on Nat Geo. The twin sisters are struggling to fit into their new home and find a ham radio, allowing them to develop a friendship with a female astronaut..
