Casey has been having terrifying hallucinations of creepy dogs and a strange boy with bright blue eyes around the neighborhood. She feels as if the child is evil and following her around. When she babysits the neighbor's children, she is attacked by their son Matty after catching him showing his sibling their reflection. Matty attacks Casey with the mirror and tells her "Jumby" would like to be born. Startled and quite shocked, she puts the boy to bed and leaves. When she meets up with a friend and explains what had happened while she was babysitting, her friend tells her of a superstition: you should never show an infant their reflection until they are a year old, or they will die soon after.
Soon more strange things begin to happen. Casey's eyes begin to change color, which causes her to become worried of a health condition, so she makes a doctor's appointment. The doctor then asks her if she was a twin and that if so her eye color changing could be completely normal. When she returns home she learns that the neighbor's infant has died.
Casey learns from her father that she indeed had a twin who died while still in the womb, when he was strangled by her umbilical cord. The news is quite startling to Casey, but she now has a theory that she is being haunted by her brother's evil spirit.
Casey meets with a Jewish woman whom she later finds out is her grandmother. She tells Casey of a story of a dybbuk who tries to enter the living world through her twin when the Nazis brought his body back to life. She killed the body so that the spirit could not re-enter the world, and now it haunts their family. This is the reason that Casey's mother had gone insane only to end her own life.
In the end, after the dybbuk is sent away, ending the life of her boyfriend, Casey wonders why now in her life did the dybbuk suddenly become active. It is then found out that she is pregnant with twins.