Rome and Ethan have been together for 14 years. He is the love her life, and she is his number one supporter. They are each other's firsts, and to their friends, they are the perfect couple. When the two begin to feel that their relationship has gone stale, they explore the idea of going open.
It's something Ethan wants to do, and it's the only way Rome feels she can keep her man. They agree that they are allowed to have sex with strangers, but they are not allowed to fall in love. In a relationship built over time, the two begin to "explore" expecting to salvage the exact same thing they are giving up.
In the end, they learn the importance of the very thing they have been blind to -- a relationship without trust will eventually crumble.