Jeff reckons Steve is still in 'The Zone' with Jane: the time after the breakup when there can still be sex, but he wants to date Susan instead. When he has a meal in a restaurant with Jane, Susan walks in.
On average, men and women think about sex every six seconds. Shorten that to every second, and you've got Coupling.
This series centers around Susan and Steve (who are a couple), and Sally and Patrick join the gang as friends of Susan (and then Steve), while Steve pulls in his best friend Jeff and his crazy ex Jane.