'Mum, there's some people here from college, they asked me back to theirs. Just for an hour or so. Is that OK?'

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 . . .