A three-part British documentary film series about life in the Paleozoic, bringing to life extinct arthropods, fish, amphibians, synapsids, and reptiles. Narrated by Kenneth Branagh and using state-of-the-art visual effects, this prequel to Walking with Dinosaurs shows nearly 300 million years of Paleozoic history, from the Cambrian Period (530 million years ago) to the Early Triassic Period (248 million years ago).

Many people think of the dinosaurs as the first inhabitants of the earth, but this prequel to the acclaimed "Walking with Dinosaurs" puts viewers in the midst of a host of strange creatures that inhabited the earth millions of years before the dinosaurs ever existed.Starting from the Cambrian Period (530 MYA) and ending at the Early Triassic Period (248 MYA), Walking With Monsters shows the life and death struggles of the fantastic creatures that existed before the dinosaurs.

Zoologist Nigel Marvin travels back in time to visit deadly creatures of the prehistoric oceans.