When Catherine Flannagan and her younger sister Margaret moved to Liverpool from Ireland in the late 1800s, they were among the tens of thousands of poverty-stricken Irish laborers and their families who left Ireland during the potato famine to find work in Britain during the Industrial Revolution. To make their money, Catherine and Margaret established and ran a boarding house. In short time, the house was filled to capacity with lodgers. But there was one problem: guests were dying in suspiciously similar circumstances.