Why should anyone want to dye a large and amiable mongrel dog black? And why should a mysterious blind stranger play one particular gypsy song on his accordian through every street in Louvigny?

To Gaby and his gang, finding the answers to these questions was a heaven-sent diversion from boredom which provided them with six weeks of intensive sleuthing. But not until they witnessed a heartrending scene in a forgotten street did any of the Ten, with the possible exception of Marion, realize what the real answer to the problem they had set out to solve would be.