24 year-old Marnie is not OK. She may just seem quiet to others, but the noise inside her head is relentless. For the last 3672 days, she has been assailed by an incessant barrage of graphic x-rated thoughts that intrude, at the most inopportune of moments, on her day to day life. Whether she's sitting exams at university, waiting at a bus stop or passing strangers on a street, her life is interrupted by irrepressible sexual thoughts. Marnie has no idea what's wrong with her. Why is she plagued by these mental images and what do they mean? Is that who she really is, deep down?

Marnie's anxiety has reached fever pitch. At breaking point, she packs a bag, jumps on the first available bus and ends up in London. She doesn't know a soul, not even herself. But the big city is the perfect place to reinvent yourself, right? Let loose in London, Marnie experiences the wonder and terror of the city unfolding itself before her; rooftop parties, impossibly crowded tubes, and midnight adventures. She soon finds out she's not the only one who's lost, however, as she meets a host of other characters who alternatively help and hinder her during her unique journey to find her real self.

Unbeknownst to Marnie as she embarks on this journey of self-discovery, she's actually caught in the grip of an excruciating form of obsessive compulsive disorder - nicknamed 'pure O' - where her obsessions take the form of intrusive thoughts, often sexual, and the compulsions are unseen mental rituals that deeply affect her daily life and her relationships.

Pure is Kirstie Swain's painfully human, sharply observed, and outrageously funny adaptation of Rose Cartwright's acclaimed book. It is a moving, warm and truthful exploration of one young woman's search for herself and her very real struggle with mental illness. It explores what it means to be a young woman today, what it means to discover a whole new world. It's about finding new friends, and most importantly, about falling in love.