Marnie has been plagued by disturbing sexual thoughts for as long as she can remember. At her wits end she hops onto a bus bound for London where she tumbles into the life of the eccentric Shereen, sardonic Amber and charismatic Joe.
Marnie attends a sexual addiction meeting, but it still doesn't explain what is going on in her mind. However, she does find a kindred spirit in recovering porn addict Charlie and gets closer to Amber and Joe by talking herself into a job.
Now that she has a diagnosis, Marnie is determined to make the most of being a single Londoner. She jumps into bed with barista Benji - but it has unexpected consequences. Charlie tries to rekindle his relationship with ex-fiancee Flora.
Having hit rock bottom, Marnie and Charlie attempt to pick themselves up. Marnie gets help from a surprisingly understanding Shereen. Amber gets the chance to interview one of her heroes and tries to resist temptation.
Encouraged by her new therapy, Marnie dips her toe into the murky waters of trusting someone with her secrets by confiding in her old friend Helen. She then brings her two worlds together in the form of a big dinner party.
Marnie is shaken by the realisation that she has pushed Shereen too far. She is convinced that everyone is turning against her now that they know about her condition. At Amber's birthday party she begins to spiral out of control.
