Nancy is hot. Hot and open-minded, which makes her even more hot.
The flatmates first meet her at a new-age dance class where her hotness compels Jez to thoughts of love and sex, although probably not in that order. She is somewhat indifferent to him, but her natural spirit of adventure demands that she tries anything at least once, even Jez.
Jez is soon grasping at concepts beyond his comprehension, such as monogamy. Turns out that Nancy’s not so hot on being faithful, and although ‘open relationship’ sounds even better than ‘open minded’ it’s not long before the hapless Jez is sidelined. At an orgy. Watching his ‘wife’ giving herself to the common good.