Who is Mr. Lamb? How does Derry get into his garden?

Explanation

Mr Lamb is an old man with a tin leg. His real leg was blown off years ago during the war. He lives all alone in his house. There is a garden near the house. It has ripe crab apples looking orange and golden in colour. Mr Lamb is sitting in his garden when Derry climbs over the garden wall to get into his garden. Though the gate is open, the boy does not use it.