At first glance, the Merryhill River appears to be a quiet place, but look a little harder …

Two families of water vole live along the riverbank. They lived happily next to each other for many years until a wall was built, which shattered their world. The battle for food and space began.

Ember Tor and Barley rush to help the water voles, but:

Can they come up with a plan to help them in time?
Will the warring families ever find peace again?
Will the voles escape from a terrifying intruder who threatens the safety of the entire colony?

Ember and Barley discover that the sleepy riverbank is not so peaceful after all.