The grey plague was a virulent sickness that hit the city of Oldtown when Grand Maester Pycelle was young. It wiped out half the city and three-quarters of the Citadel during its run. To prevent its spread, Lord Quenton Hightower ordered the gates barred, all the ships in harbor burned and anyone trying to leave killed. These orders made him extremely unpopular, however the measures were successful. The day he rescinded the orders, after the plague had burnt itself out, Lord Quenton and his young son were pulled from their horses and had their throats slit by the survivors.