Originally published in 2018 in French by Rue de Sèvres as Le château des étoiles--Tome 4: Un français sur Mars.
Summary
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.