Kate, Rachel, Rose, and Claire are all students at a private institution set on Roosevelt Island,New York City. Waking up one morning, all feel uneasy and restless as they deem strange that none of them can recall anything about the previous night. Their anxiety escalates when the school announces that Lisa, another classmate of theirs and friend to all four girls, was found dead.
Afterwards, the following night for unknown reasons the four girls are drawn by butterflies that gather them to the same place, as if they have been summoned by something which they cannot explain. There, they are approached by a woman called Lula and her partner JC to tell them all that they are already dead, and must work for them if they do not want to disappear completely. Later she explains that the girls were reanimated on new, special bodies and their real bodies are in her custody. They are revealed to be on the side of Animus. Lula also claims she has the means to eventually return them to their previous lives when their job is done. Their job is killing "monsters" in the dead of night. Lula and JC will summon the girls on certain nights, and then they will fight certain "monsters" (that look almost like regular people). After a fight the girls feel drained and tired. If they fail, they will die for real. The series also shows another character, Herve, who is trying to fight to save his cousin and his sister's lives as they are subject of a curse (that causes their complications to manifest and die), and his family are their enemies. They are the Dolore clan. It is later revealed that the two sides of the battle have Book of Curses and the reason they fight is to retrieve the book from the other side. It is because of these books that Herve's family was cursed as they stole their book from the Animus. The Animus are also cursed in that their masters have been living for several centuries. They were forced to give up what is referred to as their freedom (they are in an inanimate state) and therefore they cannot die, again the only way to lift this curse is to take the cursed book back from the Dolore family. The girls find out that if they retrieve the book from the Dolore family then it will result in them losing their memories which would mean that they could not remain with their friends and family. However, if they lose then they will die.