Heartless follows teens Sofie and Sebastian - siblings with a deep, dark and fatal secret. In order to survive they must suck energy out of other people. We follow their quest for answers as to why they are this way and their search leads them to Ottmannsgaard, a boarding school with plenty of deep dark secrets of its own

Sofie and Sebastian find out why their mother went to Ottmansgaard, but they have still got their instinctive desire to suck. Sofie’s roommate Nadja has fallen in love with Sebastian and wants him at any cost

Sofie and Sebastian discover some old paintings in the attic and learn that their secret goes many years back in time. Ditlev’s obsession with Sofie is still a problem. Can the siblings contain him? Meanwhile Sofie and Emilie’s friendship develops. It may put them both in danger. What are these uncontrollable, supernatural powers Emilie and her sister possess? And why is Just, their father, so worried about these powers?

Ditlev’s death shocks the school. Just convinces the police that it was suicide, but he knows better and starts his own investigation to identify the murder. Sofie and Sebastian are still trying to keep their secret, but know that when Nadja finds out about their curse, she will disclose their secret. Sebastian falls in love with Josefine, the serving maid. Sofie initiates a relationship with Emilie. But what if Just finds out? And who is the mysterious girl Sebastian meets in the forest?

Sebastian wants Sofie to exploit her relationship with Emilie to obtain more information about their secret. Nadja is now such a big danger that the siblings have to take drastic action to prevent her from revealing it. Josefine’s violent ex-boyfriend is harassing her and Sebastian has to deal with his presence. And just tells his daughters about their family secret from the past.