What unpleasant experience did Derry have at the bus stop ?

One day, a woman went by Derry in the street while he was at the bus-stop and she was travelling with another woman. The first one looked at him and whispered to the other thinking that Derry was out of earshot. But Derry heard her saying that she considered what had happened to him to be a terrible thing. It had given him a face that only a mother's unconditional love could stand to look at, in her opinion.