It's started in Jack's math class on the first day of school. He fell asleep and found himself in a weird place where the buildings around him looked 1800-ish. And where he finds no one except a girl holding matches
He called the girl "Matchgirl" because she doesn't seem to remember her name (We later learned that her name is Klara). After waking up from his supposed dream, he met a girl in his class named Lucy
I'll make a voodoo doll of Jack and attach it to myself
He'll be stuck here with me, therefore we can be together, forever!
Lucy and Jack became lovers over time. Jack learned that Lucy saw Klara on the day she met Jack, so they try to find out what's going on. They made a speculation that Jack will go to Klara's place on the day of the full moon
Feeling like Klara is up to something, they try to find a way of stopping Jack from transporting. Along the way, Lucy's grandfather died and she had to put Jack's and her research aside and they need to be apart for a while
And Klara is really up to something. She's planning to trap Jack with her in the spiritual world she stuck in, perhaps out of loneliness and jealousy of Jack's "friends" that kept pulling Jack and her apart.
Turned out Lucy's trip to her grandfather's funeral also gives her some insight into Klara's life before her death, but how will she use the information to stop Klara from getting a hold of Jack? Read Drawn Away