Twenty-four-year-old Marnie is witty, smart and 'normal'. Well, 'normal' apart from the relentless noise inside her head. For the past 3,723 days, Marnie has been experiencing an incessant barrage of graphic x-rated thoughts. Unbeknown to Marnie, she's caught in the grip of a remarkable form of obsessive compulsive disorder. Moving to London, Marnie is desperate to find out what's wrong with her.