Mark and Mary have been happily married for a year when Mary starts to feel a sense of restlessness in their relationship. She begins to question whether they are meant to be together forever and whether monogamy is a natural state for humans. After much soul searching, Mary decides to broach the subject of ethical non-monogamy with Mark. At first, Mark is hesitant about the idea of sleeping with other people, but he loves Mary so much that he agrees to give it a try.
They set out some ground rules for exploring their new relationship style. First and foremost, honesty is essential - they must be transparent with each other about the people they are seeing. They also agree that any potential partners must be respectful of their primary relationship and that they will always prioritize each other's feelings.
As they start to navigate their new reality, Mark and Mary find that jealousy and resentment sometimes rear their heads. They also discover that ethical non-monogamy brings with it a host of complications and challenges. While some of their experiences are fulfilling and exciting, others leave them feeling anxious and vulnerable.
The movie follows the couple as they explore the nuances of ethical non-monogamy and try to make it work in their lives. Along the way, they learn a great deal about themselves, each other, and what it means to truly love someone. Through laughter, tears, and some seriously awkward moments, they gradually discover that opening up their relationship hasn't been the disaster they feared it would be - in fact, it's opened up a whole new world of possibilities.