Elsa's parents were the greatest spies in the world, and owned a spy agency. From the time Elsa could walk she was trained to become a spy. After her parents were killed by a man named Pitch Black, Elsa grew up too fast so she could be there for her sister. She retired not wanting her and her sister to have any part of that agency, and was labeled R.E.D.
Jack Frost was found on the street and taken in by Manny Moon, the head of D.D Spy Agency. He grew up being trained to become a spy, and became the best spy at the agency. He is the leader of his group called the Big 4, which is a specialized group for people with powers. Together they have been trying to stop and ultimately take down Pitch Black, but he is always one step ahead of him. When Manny comes and tells them Pitch is looking for a new secret weapon, they are shocked. Even more shocked to find out that weapon is a person, and ex-agent actually. They are supposed to protect this person with their lives if necessary and recruit them.
Issue is this person doesn't want to be recruited, and is much more special that the eyes can see. This person may be retired, but she is extremely dangerous.