Midsummer 2017: teenage mum Tallulah heads out on a date, leaving her baby son at home with her mother, Kim.
At 11 p.m. she sends her mum a text message. At 4.30 a.m. Kim awakens to discover that Tallulah has not come home.
Friends tell her that Tallulah was last seen heading to a pool party at a house in the woods nearby called Dark Place.
Tallulah never returns.
2018: walking in the woods behind the boarding school where her boyfriend has just started as a head teacher, Sophie sees a sign nailed to a fence.
A sign that says: DIG HERE . . .