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 hits another dead end when she goes to a sex addicts meeting, but she finds an unexpected kindred spirit in recovering porn addict Charlie.

Marnie is determined to make the most of being a single Londoner now she knows what is wrong with her. She jumps into bed with Benji an earnest, clingy barista, but it has consequences at her work.

Marnie and Charlie try to pick themselves back up after hitting rock-bottom. Marnie gets help from an unexpectedly understanding Shereen while Charlie tries to prove he's up to his old job.

Encouraged by her new therapy, Marnie tries out trusting her old friend Helen with her secrets and brings her two worlds together at a big dinner party. What could possibly go wrong?