Magical medieval artifacts are on display at the Los Angeles County Museum of Art. They are the perfect target for magical thieves. Look out Lucy Heron. It's not the usual menace looking to steal a strange magical crown. Good thing Lucy and the Silver Griffins are on the case. Meanwhile, the Underfoot Brigade are on a case of their own. Monsters are in the underground tunnels. Time to find out why. The answers to both problems are hidden in plain sight. Can they look to the past to solve the riddle of the present? Good thing the Heron family is good at researching history-including their own. Will they be able to get the answers they need in time? Will Lucy, the Herons, and the Silver Griffins be able to protect the artifacts and the City of Angels as more artifacts are revealed?