A shy student trying to reach his family in Ohio, a gun-toting bruiser in search of the last Twinkie and a pair of sisters striving to get to an amusement park join forces in a trek across a zombie-filled America.

Returning to her home planet Pandora, an infamous bounty hunter forms an unexpected alliance with a ragtag team of misfits. Together, they battle alien monsters and dangerous bandits to uncover one of Pandora's most explosive secrets.