David Barr calls upon Diamond to discuss a business arrangement. He wants him to guard his store, a most fashionable haberdashery and tailoring shop that had been vandalized two nights ago. The only item missing was one blue serge suit. This was not the end of the trouble when the following night the store was broken in to again and the whole stock of blue serge material was stolen and a grey flannel suit left untouched. Barr wants Diamond to solve the mystery of this unusual robbery.