Castle in the stars. Book four, A Frenchman on Mars

Summary/Review: "As Seraphin, Hans, and Sophie make their descent to the Mars surface with stowaway Loïc and the wicked Gudden in tow, they're prepared for danger. But with its gravity-defying rain and giant carnivorous beasts, Mars is even more treacherous than they expected. When Seraphin suddenly finds himself separated from his friends and alone in the Martian wilderness, he must trust a mysterious shape-shifting creature to guide him back to safety. But this creature has an agenda of their own."--Provided by publisher.