Three brothers who live in a tall, narrow house in town, cared for by a variety of people decide to go off on their own to find an uninhabited island.
The brothers think the elderly boy is a bore; he isn't really interested in adventure and is afraid to let the land out of sight. In spite of him they find their island, and go exploring.
The boys set about cleaning the cottage they have discovered on Grasshopper Island.
The boys decide that they would like eggs for breakfast, so they set out to find an egg tree.
The find of a chick brings further new adventures and secrets...
Life on Grasshopper Island is almost becoming dull, so the boys go exploring.
Mouse has a plan to cross the island without getting lost. He wants to surprise the others...
Cornelius Button throws away his old cheese - and the boys think they have discovered buried treasure!
While he's making a map of Grasshopper Island, Smarty discovers The Big House. He walks in through the front door just as Cornelius returns. So the Island is inhabited after all.
Cornelius Button's sister is coming to visit the Island, so Lupus goes to clear up the cottage for her to stay in. There, the boys are astonished to discover her.
The boys find Grasshopper Island unexpectedly lonely. Smarty decides to make wine. Making it is certainly fun - but drinking it is another matter.
When Mouse is swept out to sea on an oil drum he has found on the beach, Cornelius Button rescues him. Lupus's secret is out; the boys are discovered. But instead of being angry, Cornelius Button is delighted.
Cornelius claims that long ago he discovered a rare blue grasshopper.
