Hours after the failed assault, Marck reaches Supply at the top of the down deep with the other survivors. The landing is tense and chaotic: no one knows how badly the last explosion slowed IT, news of McLain's death has spread, and the people of Supply are openly hostile to wounded mechanics. Marck, still half deaf and injured, searches for Shirly and is relieved when she suddenly finds him alive.

Shirly examines Marck's arm and tells him she thinks bomb fragments are embedded in it. Marck confirms that Knox and McLain are dead, while Shirly admits she feared he had been killed. As shouts rise from above and Supply retreats into its doorway, Marck and Shirly leave with the rest of Mechanical, deciding their only safety lies farther down at home.

When they finally reach level one-thirty-nine and the entrance to Mechanical, Marck discovers that the crew who stayed behind have sealed the security station with welded steel plates. Only a tiny gap beneath the turnstile has been left open, forcing refugees to crawl through one at a time. The bottleneck turns deadly when Security officers above begin firing down into the exposed crowd, wounding and scattering people as those inside Mechanical keep shouting for order.

Seeing the crowd trapped, Marck sends Shirly back toward the stairs for cover, then runs upward with his rifle to stop the shooters. Marck kills one Security man firing over the railing and then shoots another as the officers try to descend on him. Marck retreats toward the Mechanical entrance, but Security gunfire hits him in the back before he can escape.

Mortally wounded, Marck crawls to the floor near the narrow opening. Shirly, already being pulled through into Mechanical, reaches back toward him and screams, but Marck tells her to go and says he loves her. Shirly disappears inside just before the last helper in yellow is shot, and Marck dies outside the sealed entrance after helping secure Shirly's survival.