The Walking Dead: The Oath (2013 ​ - 2013)

This series tells the origin of the "Don't Open, Dead Inside" paint on the cafeteria doors of the hospital Rick Grimes awakes in, post-apocalypse. It follows Paul and Karina as they escape their zombie-overrun camp in search of a medical station. The central theme of the series examines the will to persevere in the face of inevitable death.