Reports of an attack on a swimmer in a lake close to Berlin is the starting point for an intense and shocking investigation. Wade travels to Germany where he meets modern-day victims of a beast that has been raising its snout above the surface of fresh waters in Europe regularly over the past 700 years. Investigations travel to Spain where Wade discovers firsthand that the wels catfish is a living, breathing aggressive predator growing to man-eating proportions capable of everything depicted in medieval records and more.