The year was 1765. Eminent botanist Philibert Commerson had just been appointed to a grand new expedition: the first French circumnavigation of the world. As the ships' official naturalist, Commerson would seek out resources--medicines, spices, timber, food--that could give the French an edge in the ever-accelerating race for empire. Jeanne Baret, Commerson's young mistress and collaborator, was desperate not to be left behind. She disguised...