On the western frontier, three bounty hunters named McGraw, Wilcox, and Valentine are searching for their prize, "Undertaker" Harvey, a notorious bank robber and killer. The frontier is never a friendly place to begin with, as they encountered a dead sheriff in a small town, killed by the Jeffs twin brothers. The trio offers their service to dispose the two criminals in return for food and shelter before going on their search for their target.
They eventually tracked down Harvey and a skirmish engaged, Harvey was shot in the fight and is forced to flee. The bounty hunter pursues their bleeding target and follows the blood trail as they wipe out Harvey's henchmen in the process. Harvey's wound turned out to be mortal. As the gang leader slowing bleeding himself to death, a mysterious man appears and offers him a chance for revenge against the three bounty hunters.
As the party lost the blood trail, they met "Dutch" Quimby, Harvey's second in command. After learning about Harvey's injury, Dutch immediately seeks her boss while her gangs is holding off the trio. Dutch soon find Harvey, who, much out of Dutch's surprise, turn out to be fine. Harvey then order the gang to go to a small farming village. This confuses Dutch, as she does not understand why the gang is heading to a village with little wealth.
By the time the bounty hunters arrives in the village, they find all the inhabitant slaughtered. One villager in his dying breath told him that Harvey's gang arrives at the villages and start killing them without questions. As the gang is puzzled by Harvey's action, they find Crazy Jake, Harvey's loyal explosive man and escaped convicts, is waiting for them to come. After a brief fight, they follow Jake's trail to a small frontier outpost, where they had captured and using its steam technology against the trio. Learning that Harvey is equipped with this new technology, the three concerned about what Harvey's gang is now capable of.
Eventually, they cornered Jake and successfully eliminate the mad scientist and set out for others. The group is wondering why a robbery gangs had begun killing everyone they saw without any intention for wealth. At the same time, Harvey's strategy had demoralized the gangs and forced Dutch and the majority of the gang members to leave. Yet, out of loyalty to her former boss, Dutch decides to lure the trio away from Harvey as she could. The three bounty hunters chased Dutch and her flying gangs, facing ambushes and airborne vehicles, they finally cornered Dutch and captured her. Dutch then told the gang of the reason of her desertion and Harvey's current location.
Upon finding Harvey, the group is shocked to see undead hordes surrounding Harvey and under his command. After driving off the relentless assaults of the unearthly beings. The three realizes that they stand no chance against Harvey's newfound army. McGraw suggests they should enlist the help of his acquaintance, Clive, who is a skilled monster hunter at the frontier. After driving back the undead army along their way, they find Clive is waiting for them. Clive informs the group that the undead activity had been unusually high recently, and agrees to McGraw's request for help. Together, they set out to find Harvey. On their way however, they encountered an undead vampire named Nadia Romanov, who allied with the protagonists due to having Harvey as their common enemy.
Following a series of battles, Harvey's army are decimated and is once again back to a corner. With the help of Clive and Dutch, the trio launched a final blow on Harvey and killed him. After the battle, Dutch left the gang while Clive offers to escort them back to civilization. The group could not help but wonder over all the things happened during the hunt for Harvey.
All of a sudden, they noticed that the group is surrounded by hordes of undead commanded by the mysterious man. Upon witnessing the group ability to kill Harvey and his undead hordes, the mysterious man deems the group a threat to be eliminated. Facing the new-found threat, the group find themselves surrounded by undead being coming to their position and is forced to eventually make a last stand. In desperation, Romanov arrives to offer her help and telling them the mysterious man's identity: Edmund Ghast, a necromancer who seeks to rule the frontier with his undead army. Using Harvey as his pawn, Ghast gathers the dead inhabitants from Harvey and turn them into ghouls. In exchanges, Harvey is able to command a portion of the undead to exact his revenge. Facing with no option, the group is forced to ally with the vampiric huntress for their survival and set out to kill Ghast before the hordes overwhelm them.
After a brutal battle, the group finally defeat Ghast and killed him. Seeing their common enemy is gone and the frontier is safe from undead hordes once again, the alliance is disbanded and the trio return home once again, wondering about the future of the frontier, as well as theirs.
