Following a pioneering marine biologist—one of the first women in her field and among the first humans to explore the ocean’s twilight zone—as she descends 3,300 feet into its darkest depths. From capturing the first-ever footage of the elusive giant squid to uncovering the glowing mysteries of deep-sea bioluminescence, she embarks on her most daring quest yet: documenting a phenomenon that could transform our understanding of life on Earth.