On Christmas Eve 1913 in Calumet, Michigan, more than 400 people packed a second-floor party during a brutal five-month copper strike. Someone yelled fire when there was none, and in the stampede down a steep staircase, 73 people died, 59 of them children. This episode examines the disaster known as the 1913 Massacre and the century-long battle over what actually happened in that stairwell.

We set the scene with the war of attrition between the Western Federation of Miners and the Calumet and Hecla Mining Company, then walk through the crowd dynamics and compressive asphyxia that made the staircase lethal. We dismantle the enduring myth of inward-opening doors using architect's blueprints and contemporary records, and trace how the tragedy was weaponized by both the union and the anti-union Citizens Alliance.

• Why the building's o ...