Jeremy Wade is on the trail of horrifying killers from the depths of time. Fearsome, prehistoric beasts are brought back to life using cutting edge technology and recently unearthed fossils in a quest to find the greatest river monster of all time.

In Fiji, people are coming under attack from unseen assailants in the water, but it's not clear if there are multiple culprits, or a single persistent perpetrator. Jeremy Wade battles tropical storms and thick jungle in an all-out search for a culprit.