Marinette and her friends are still learning how to be heroes. Their previous journey led them on a wild path in which they discovered their powers and learned to harness them. Now a year later, they are living on a secret base with some old and new friends preparing to fight Amber once again. This time however, Amber has teamed up with a powerful villain from the past. The heroes will have to learn to work as a team with some new allies in order to defeat this old and new enemy. The task will not be easy as the heroes find themselves face to face with new challenges along the way. A shocking continuation from the first book Becoming Heroes: The Story of the New Guardian.