From the extreme north of South America, freshwater detective Jeremy Wade hears rumors of a body-snatching spirit said to drag men deep into the river, never to be seen again. A predatory freshwater mermaid, locals call her the Water Mama. She may be a beast of mythology, but the carnage she leaves in her wake is all too real. People are disappearing without trace, one-by-one from these waters and Jeremy is convinced there is a flesh and blood River Monster lurking behind the legend of the Killer Mermaids.