It's not okay to cheat on someone that trusts you.
Marcus has been in a monogamous relationship with Sara for a year, but Sara's friend Jen keeps flirting with him.
Marcus wants to feel loved.
Marcus has a romantic dinner with Sara.
Marcus has a romantic dinner with Jen.
Sara enjoys a loving relationship with Marcus and stays friends with Jen.
Sara discovers Marcus cheated on her, breaks up with him, and ends her friendship with Jen.