When the zombie apocalypse struck, intrepid American bulldog Riley quickly discovered it was up to her to keep the pack safe. As well as Yorkshire terrier Ben-Ben and previous archenemy Patches the cat, Riley helped to keep carefully the zombies away while favorite human Jessie journeyed cross-country to discover protection for herself and her baby brother, Zachary.

But after a long journey, Riley and the gang arrive in Las Vegas-one from the few remaining inhabited cities-only to find that it has been taken over by a group of thugs who rule through dread and brutality. Making matters even worse, ruler Icely and his gang have taken to staging pet dog fights as well-known entertainment, and Riley catches their eyes. With Riley pressured to fight for her life and Jessie locked up in the home of Icely himself, the near future is uncertain. Can Riley save your day once again and help her pack escape to safety?