In 1997 a terrifying sound was picked up by underwater microphones once used to track Soviet submarine movements in the ocean. This sound was picked up over five thousand kilometers away, and was rumored to be a large creature. In 2019, the sound has returned and its source is no longer a rumor. A team of engineers builds a vessel and prepares to attempt to locate and make contact with the entity. Meanwhile, Codi Cohl is entering a darkness of her own. She receives bionic lenses just before perfect blindness befalls her. With her new version of sight, Codi may be the perfect candidate for the dive crew. But her fear of the darkness might envelop her before the cold deep water of the ocean gets its chance.