Into the Drowning Deep is a 2017 science fiction horror novel by Mira Grant. It is the follow-up to her 2015 novella Rolling in the Deep. It focuses on Tory Stewart, a sonar specialist who becomes obsessed with mermaids after her sister's disappearance. Tory's sister Anne worked as a reporter for Imagine Entertainment. While filming a mockumentary about mermaids, the crew of Imagine's ship Atargatis vanished. Tory vows to discover the truth about what happened to her sister. Source: Wikipedia (en)