Dave and Abigail have the perfect relationship. They are more than husband and wife, they're best friends, with an active sex life to rival even the youngest of couples. The two of them can talk about anything, even their wildest fantasies, but they're rapidly running out of ideas to keep things spicy in bed. When Dave broaches the subject of attending a swinger's party Abigail is willing to give it a try. The end result is nothing short of disastrous. Abigail thinks trying a threesome would be better. She even has a person in mind and with her fortieth birthday rapidly approaching she decides to give it a go. Little does she know that Dave already has birthday plans of his own. When they both come home with an extra partner their threesome quickly turns into a foursome and as the clothes come off the sexual intensity skyrockets. Everyone's fortieth birthday should be this good.