Deputy Rick Grimes wakes up from a coma in an abandoned hospital after surviving a shooting. Outside the hospital the world is a nightmare, the dead have re-animated. Walkers, as they're called, are everywhere. After meeting a man and his son, Rick learns that his wife and son (Lori and Carl) may have fled to Atlanta, where the Center for Disease Control has set up a quarantine zone. He arms himself and sets out for the city.

Rick's best friend has helped Lori and Carl survive, and they are living just outside of Atlanta in a makeshift camp for a handful of survivors. Rick arrives in Atlanta to find it completely overrun by walkers. He's rescued by people from the camp and reunited with Lori, Carl, and Shane. Rick assumes control of the group and following an attack by a horde of walkers, they flee for the CDC.

At the CDC, they find one surviving doctor. He knows a bit about the pathology of the virus, but has no cure. Before long the CDC building activates safety protocols as it runs out of fuel. Rick's group barely manages to escape before the building incinerates.