The children bring Alice to the District 1 medical center for help. As Scarlet examines her, Don arrives, now fully infected but still conscious. He watches as soldiers try to restrain Alice (who is terrified, not violent). In a fit of rage, Don attacks a soldier, vomits blood into the soldier's eyes , and instantly turns into an Infected. The containment fails. Within minutes, the tightly packed Green Zone is overrun. Act Three: The Fall of London Code Red: General Stone orders "Code Red"—exterminate all civilians and infected in District 1 to prevent the virus from spreading. He locks down the zone and orders napalm strikes.

Don decides to risk going to a nearby farmhouse to scavenge. Before leaving, he kisses Alice goodbye. While he is gone, a young infected boy stumbles into the cottage. Jacob tries to calm the boy, but the child turns violently, vomiting blood into Sally's eyes, infecting her instantly. Chaos erupts.

A moment of silence. Then the radio operator says the final, terrifying line:

"...God help us all."

The group surfaces to find the city in chaos. They steal a car. Hot on their trail is a now-supernatural, relentless Infected: Don . Unlike other Infected, Don retains a twisted form of memory and purpose. He relentlessly pursues his own children, not just mindlessly attacking but hunting them with a terrifying, personal rage.