It's 1997 and Tanya is a high-achieving sixth-former at an exclusive private school, blessed with a comfortable middle-class lifestyle and a close, loving family.
But at weekends the dutiful daughter and model student is replaced by a reckless thrill-seeker who pulls drug-fuelled all-nighters in acid house clubs.
Tanya thinks she has her double life under control.
But soon the drug-induced mood swings take a more sinister and dangerous turn, as she lurches between depression and exaltation.