Twins Arthur and Rose loved staying with Grandad and would spend days in the Land of Roar where dragons, mermaids and ninja wizards kept them safe from the sinister scarecrow, Crowky.

Now they are 11, Rose spends hours on her phone and worries about fitting in and Arthur, despite the scar on his wrist where he was bitten by a dragon, has almost forgotten about Roar. But then a mysterious figure appears at the attic window, an old map turns up, and Grandad vanishes...

It seems ridiculous but could Roar be real after all? And can Rose and Arthur find Grandad before he is lost forever?