Clarissa Fray (Lily Collins), a seemingly conventional young lady leads a routine life attending poetry sessions and club-hopping with her best friend Simon (Robert Sheehan) while she stays with her artist mother (Lena Headey) in Brooklyn.
Suddenly one day, strange and inexplicable things start happening to her. On a date with Simon at a pub, she witnesses a murder that apparently only she can see. Distraught, she rushes home and soon enough, she inexplicably doodles a symbol that gets her mother worried. That symbol has something to do with the other world. There is a past that her mother is holding back from her.
Meanwhile, she is being followed by Jace Wayland (Jamie Campbell Bower), one of the murderers from the club. On questioning him, as to how is it that only she can see him, he tells her – “Because you are not a mundane.”
“What is a mundane?”
“Someone from the human world,” he answers. Confused and taken aback, she does not know how to react.
Around the same time, she gets a frantic call from her mother. When she returns home, she finds her apartment ransacked, her mother missing and she is attacked by an unusual creepy creature.
From there begins her adventure of finding the power secret, “The mortal cup”, which her mother had apparently hid to protect it from the villains.