The opening chapter picks up where Episode One left off. The Citadel Core gave out as Alyx and Gordon were leaving City 17, and the resulting shock wave has derailed the train in which they were traveling on. Gordon and Alyx survive the crash, and Alyx retrieves the Gravity Gun in order to free Gordon from the wreck. The ruins of City 17 are visible, with a Superportal forming above the collapsed Citadel. A portal storm occurs, appearing to emanate from the Citadel ruins, destroying the damaged rail bridge and opening a path into a mine shaft for Alyx and Gordon to follow.
