Cecily was born as the only daughter of an English steelworks manager based in the Rhondda Valley in southern Wales while her mother was of Welsh descent. Cecily went on to marry Ethan Frye and joined the Assassin Brotherhood, the couple undertaking missions for the Assassins together. They also acted as the superiors of the Assassin George Westhouse, whom they trained and ran missions with.
On the 9th of November 1847, Cecily gave birth to Jacob and Evie, but died of complications shortly afterwards. A depressed and mourning Ethan traveled to India after accepting an offer from Cecily's mother to raise Jacob and Evie until the age of six.