What can you do when fate deals you an unfair hand, when purely by chance life delivers a devastating blow? Do you have it in you to fight back even harder? 48 Hours explores how people struggle with difficult circumstances. Battling A Brain Tumor: Correspondent Susan Spencer reports on David Bailey, a young go-getter who re-thought his life after being stricken with a brain tumor. In The Dark: Sunlight can kill 8-year-old Katie Mahar. She has XP, a rare and often fatal disease. Susan Spencer describes how she and her family have coped. Saving Amy: Correspondent Jerry Bowen provides an update on 12-year-old Amy Frohnmayer, who has a rare genetic disease called Fanconi anemia. She has just one defective gene but it prevents many of her cells from growing normally. Will she survive?