It is the early 1900s and the three Francoeur children are struggling to survive in the slums of Paris. But their lives change forever with the arrival of a mysterious stranger from their father's past. Countess Aristophania Bolt from the Kingdom of Azur claims she has come to help the trio, but between disturbing phenomena—tricks or sorcery?—and invisible threats, it is hard to know whom to trust...

The secret war of Azur is growing in ferocity. Countess Aristophania Bolt is banking on the three Francoeur children to turn the tide, notably by discovering the legendary Aurora Spring. Basile, Victor, and Calixte are determined to prove Aristophania right, but it may be too late—their allies are dwindling, and the Banished King and his minions are closer than ever.

The fate of the secret Kingdom of Azur hangs in the balance, as does that of the world as we know it. Aristophania Bolt is racing against time to thwart the Banished King and find the key to salvation: the Aurora Spring. Along the way, she receives lots of help from the talented if unpredictable Francoeur children. But challenges are mounting, in the form of beguiling foes, a painful past that won't stay buried, and the mysterious Red Mountain, which is polluting bodies and minds. Will their efforts be enough to avoid a future ruled by black Azur?

The Banished King's plans for widespread insurrection and destruction are nearing fruition. Victor and Calixte, on the cusp of finding the miraculous Aurora Spring, have reached a dead end. And Basile appears to have abandoned his family in favor of the enemy camp. With the walls closing in on her and no allies apart from the Francoeur children and her trusted valet, will Aristophania be able to use her powers—and her instincts—to save the Kingdom of Azur?