MASS hysteria, incest and sexual experimentation are all explored in this twisted coming- of-age film with a hint of the supernatural by director Carol Morely, who’s got a track record as a documentary film-maker.

Set in 1969, it centres on best friends Lydia (Maisie Williams) and Abbie (newcomer Florence Pugh) who attend a strict girls’ school somewhere in the English countryside. When tragedy strikes,a mysterious epidemic of fainting fits— led by the troubled Lydia — breaks out. 

Is something truly wrong or are Lydia and her clique faking it? That’s the question at the heart of a drama which starts off promisingly before plunging into pretentious and “meaningful” territory.

Williams (Game of Thrones) gives a sterling performance as a bolshie 16-year-old while Pugh is captivating as the charismatic Abbie.

But Maxine Peake is somewhat wasted as Lydia’s mother — an agoraphobic hairdresser — and Greta Scacchi is totally unrecognisable as the stern deputy head.

Morely attempts to add mystique and a supernatural vibe with a nature subtext involving arty shots of trees and river banks which completely miss the mark.

Her exploration of mass hysteria among teens gripped by raging hormones has its fascination but the finale doesn’t live up to the intriguing scenario preceeding it.