The Gospel Truth

Om and his family, in Chandigarh, have to welcome an unwelcomed guest on Amy's seventeenth birthday. But the guest has already planned to spoil the party and to make their lives hell.
In the meanwhile, another school going girl goes missing while returning from the school in the vicinity of Lucknow, making the count to three in a year.
What is the plan of the guest?
Why are the girls missing? And who is behind these missings?