Short and sweet book. With a lot of humors a 9 yr old would enjoy.
Playing with words and being clueless is how Tim Diamond worked on a case.
A spy came to the office and asked to use the telephone. The brothers had no money and didn't pay the phone bill. So, they asked the spy to use a phone box outside.
A bullet had flied in the office in the meantime and harming no one.
So they followed the guy outside only to find him killed by another bullet.
They wanted to report this to the police but they have no money for the bus fare. It took them half a hour of walking. The police didn't believe them at all so they went back to the scene of the crime only to find both the body and the phone booth gone.
It is that kind of a story.
Really enjoyable read, even for an adult.
Reading this for Halloween Bingo