When Danny's twin sister decides to come to Hawaii to spend time with her brother and niece she doesn't think about an old friend of her's that she hasn't seen in 9 years. Then again she had good reason for that. How is her life going to change when she sees Steve McGarrett and he learns her "little" secret that she has kept from him for nine years.

When Alyssa's parents were killed, she had no one to turn to except her cousin ,Catherine who was working with five-o. Although Alyssa had some secrets about her that even Catherine didn't know.