A former Apache pilot, Hannah Banks, had been leading a group of survivors across the Chicago landscape, when their car's badly rotted battery gave out. With no transportation, they had to flee on foot as a horde of walkers emerged from the many suburban houses that make up the West Sunset Avenue area. Managing to escape to the relative safety of a long since abandoned house, they hunkered down.
Not long after their arrival, they spotted an ambulance out on the road, with its hood popped up: looking through his sniper scope, Oskar - one of Hannah's group - spotted what looked like a viable battery in place. With this in mind, they made a move on the ambulance with the aim of retrieving the battery, and using it to power up one of the many abandoned cars on the road.
Before they got there however, a girl - Kylie - jumped into it first, scavenging for medical supplies. Not knowing if the girl was friendly or not, Hannah and her group surrounded and the ambulance and ordered her outside. After a brief chat, they decided she was friendly and no drama resulted. However, the battery in the ambulance was a dud, but before the group could withdraw, Camellia (another of Hannah's group), appeared from behind a fence. She had found a car battery in good condition, but had to fire her rifle to escape her undead perusers - ringing the literal dinner bell for the dead.
The fence came down under the weight of dozens of walkers, trapping Camellia. Woodrow, the fourth member of Hannah's group, ran to intervene with the assistance of Kylie. Hannah and Oskar fled, however, not prepared to risk their lives or bullets for what they perceived as a lost cause. Woodrow was bitten in the ensuing rescue attempt, but managed to get Camellia to safety, before waging a one man war with the endless horde. As he did so, Kylie helped Camellia get away.
Meanwhile, Hannah and Oskar sought refuge in a nearby house. They were debating leaving the two girls to die, when one of the house's former occupants attacked from nowhere. Hannah fired her rifle, ending any hope of allowing the dead to eat the two girls and leaving them be. This forced Hannah to go on the offensive, and she charged out of the house guns blazing, making her way to the girls. Oskar followed, but proved little help.
The group then ran on down the road, into East Sunset Avenue, where they have happened upon a long since abandoned CDC Safe Zone based at St. Timmothy's church. There is a humvee there, which appears in good condition, and the group now plan to use the vehicle to mount their escape. The horde, however, are not far behind.
There y'ar. It's a bit long, but I made it as short as I could.