Unsanitary conditions and small, densely-populated spaces made the Close a perfect breeding ground for Yersinia Pestis, better known as the Plague. It broke out in Edinburgh in 1645, and Mary King’s Close was struck hard. The council moved away the people who were healthy and able (or willing) to relocate. The remaining sick and poor were instructed to stay in their homes, and the Close itself was sealed to stop the infection from spreading further. For many, their homes became their tombs as they succumbed to the pestilence.