When she was very young, Fiachra had a twin sister named Aoife. The two of them were inseparable from the start, even though they were quite different. Fiachra was quiet and thoughtful, about as serious-minded as any five-year-old could be. Aoife, on the other hand, was bold and adventurous, and absolutely determined to explore the world around her. Because their mother was busy looking after their new-born sister Niamh, it often fell to Fiachra to look after Aoife and make sure she didn't get into too much trouble.
Then came the day when Aoife decided to explore the forest near their house. Their mother had forbidden them to go anywhere near it. Outlaws often camped there, and it was too easy for young rabbits to get lost in the trees. Unfortunately, this only made Aoife more curious to see it, and when both Fiachra and their mother were distracted, she slipped away. Of course it didn't take long for Fiachra to notice. The best way to tell when Aoife was getting into trouble was when things got quiet. It didn't take long for Fiachra to guess where Aoife had gone after that, and even though it went against an unspoken agreement that had held throughout their lives, Fiachra went to Bébinn for help.
Long after she was grown, Fiachra would still occasionally wonder if things might have been okay if she had set out after her sister right away, instead of taking the time to fetch their mother. Bébinn and Fiachra's step-father Liam spent the next three days looking for Aoife in the forest, but it was Fiachra who finally found her. Going against all her mother's wishes and warnings, Fiachra went to the forest herself, to one particular cluster of oaks where she and Aoife had played once before. It was there she found her sister lying against one of the trees with her neck broken and a scrap of bright yellow cloth clutched in one hand. No-one was ever found. No explanation was ever given, though even then it was easy enough for Fiachra to guess what had happened. Aoife had stumbled across some brigand hiding in the trees and he had valued his continued freedom over her life. After almost thirty years, the pain of losing her has been dulled somewhat, but every time Fiachra looks at the locket that was meant for her sister, she still remembers.