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.

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?

Marnie is shaken when she realises she's pushed Shereen too far, and starts to become paranoid that everyone has turned against her now they know about her condition