After the events of last summer, Amelia and William are strictly not allowed to have anything to do with treasure. As soon as they arrive in New Orleans, where they are spending the summer visiting Samantha, Amelia's aunt, Amelia shows William a crumpled note she has received with a new mission for them. They need to find a missing locket belonging to a certain Lucille LeBlanc. As they read it, they know that they are going to have to break the rules. They also know nothing about New Orleans or Louisiana, which will make hunting very difficult. But where better to start than in the huge library in Samantha's house…?