Kate de Vries is Matt Cruse's love interest. She's depicted as a very bold and strong-willed character, often speaking her mind bluntly. She’s also very intelligent and clever, but she can also be headstrong, which can land her — and sometimes her companions — into trouble. Her parents and chaperone constantly scold her for things such as speaking out of turn, and saying or doing things unbecoming of an obedient, aristocratic young lady.
Against her parent's wishes but inspired by her grandfather, she aspires to be a groundbreaking zoologist, believing there to be life in the skies. Although she is wealthy, Kate is a female in a patriarchal society, and must struggle to receive the attention and respect she deserves - things that would automatically be bestowed upon her if she were male. Her interest in zoology is frowned upon by the majority of the male-dominated Zoological Society. Her groundbreaking discoveries are dismissed as hoaxes by other zoologists, such as Sir Hugh Snuffler, despite overwhelming evidence to the contrary, such as photos, skeletons, and even live specimens.
Kate is a teenager with pale skin, long mahogany hair, and dark, expressive eyes. She usually has a very carefree aura but has to act like a poised and proper lady when necessary. She dresses in fine clothes and acts sophisticated when eyes are upon her, but at other times is an adventurous girl with a bit of a disheveled look. The latter, more relatable appearance is when Matt finds Kate to be the most attractive.