The unburied dead are returning to life and attacking the living to kill and eat them. The first part of the film follows the actions of former Colonel and current Sergeant "Nicotine" Crockett (Alan van Sprang). In the opening scene, Colonel Crockett, after a failed raid of sorts that ends in the deaths and reanimation of several fellow National Guardsmen and his getting demoted to Sergeant, deserts his post with fellow soldiers Kenny (Eric Woolfe), Francisco (Stefano Colacitti) and Tomboy (Athena Karkanis). The four fugitive soldiers go on where they rob the protagonists of the previous film (see 'Diary of the Dead').
Meanwhile, off the coast of Delaware lies Plum Island, home to two Irish-American feuding families - the O'Flynns and the Muldoons. The former family, lead by Patrick O'Flynn (Kenneth Welsh), rounds up a posse and kills the undead of the island, learning that the Muldoons, led by Seamus Muldoon (Richard Fitzpatrick) are keeping their undead loved ones "alive" until a cure is found. A brief standoff ends with the Muldoons exiling Patrick and several other O'Flynns, under the suggestion of Patrick's daughter Janet (Kathleen Munroe).
Three weeks later. The four National Guard deserters find themselves joined by a young teenager known only as Boy (Devon Bostick) after an encounter with some fellow zombie-killers whom the four rogue soldiers are forced to kill when the hunters attempt to kill them as well. Crockett and his group steal an abandoned armored truck nearby and decide to drive north to Canada. Through Boy and an Internet connection they learn of Plum Island - a video that was recorded by Patrick O'Flynn. They head to a nearby dock off the deserted interstate highway as instructed, and a gunfight starts between the O'Flynns bunkered down in a fishing shop and Crockett's group. Francisco jumps off the pier and swims out to a large ferry steamer, successfully commandeers the unmanned ship for the group. During the battle, several zombies showing up to distract both sides of the gunfight. Francisco is attacked by an underwater zombie which he successfully battles, biting the finger off of an attacking zombie along the way.
The O'Flynns, except Patrick, are killed and eaten by zombies and the four Army deserters board the ferry. Patrick too jumps aboard, kept there by a shaky truce of sorts as the rest of the group takes care of the zombies on board the ferry. Francisco starts to feel sick, having earlier ingested the blood of a zombie when he bit off the finger of the underwater zombie that attacked him. On the trip over, Patrick reveals he delibrately sent other strangers over to Plum Island to anger Muldoon and trigger the latter's distrust for strangers. Eventually, the group stops the ferry a short distance away and makes it to the island on a small dingy.
There, they discover that the Muldoons have chained up the zombies in imitation of their previous lives - a mailman puts mail in a mailbox, a logger wields an axe on some wood, and so on. It is revealed that Patrick's daughter, Janet, is now a zombie, riding around on her horse as she did when she was alive. Not only that, but the living strangers sent over by Patrick have been killed by the Muldoons in order to 'feed' them to the zombies while the strangers who arrived as zombies were allowed to remain animated. Patrick is disgusted with this and, as he attempts to go into town and gather some allies that did not leave the island from his family, two scouting Muldoons attack the deserters, shooting Crockett and Kenny. The latter dies from his wounds, and is shot in the head by Patrick to prevent reanimation. Patrick heads off.
Taking shelter in an abandoned meeting house, Boy works to stitch up Crockett's gunshot wound on his left shoulder, Francisco's sickness gets worse and he wanders off where Tomboy finds him and he asks her to shoot him before he turns into a zombie. She complies, and is then captured by Muldoon men and taken to his headquarters across a small bridge leading to the other part of the island. It is now revealed that Janet is, in fact, a twin: Jane, her favored sister, is the zombie on the horse from earlier. Janet helps Crockett out, and she, Crockett and Boy join the O'Flynn group for their attack on the Muldoons. Crockett agrees to come along to exact revenge for Kenny.
A standoff occurs at the bridge of the river that separates the two families' land, and the O'Flynn group with Crockett are captured, while Boy and Janet are pushed off into the forest. Tomboy is released from Muldoon's capture (During her capture she also learned that Muldoon's own wife is now a zombie that he keeps chained up in his kitchen) and rejoins the captive group. Muldoon and O'Flynn face off. Muldoon's one wish is to prove O'Flynn wrong about the zombies, hoping to get the creatures to eat something other than human flesh. Muldoon's latest example is Patrick's daughter Jane, attempting to get her to devour a horse. A farmhand, Chuck (Joris Jarsky), brings out a herd of captured zombies to watch the zombie Jane's attempt to eat the horse.
She doesn't, and Janet returns with Boy, giving Crockett and the O'Flynns their weapons back. Janet attempts to reach out to Jane, who bites her twin sister on her hand. A climatic gunfight erupts between the two families. Chuck switches sides and gets shot by Muldoon for his trouble. Dying, he releases the zombie herd and is devoured. The gunfight's focus changes to the zombie threat, and they eat and kill most of the ones involved in the shootout.
Muldoon and O'Flynn, each with one bullet left in their guns, create a shaky truce that is immediately broken by Muldoon shooting O'Flynn in the back. A dying O'Flynn unleashes a secret gun stored up his wrist and kills Muldoon. Crockett and his group, fed up with all of the death, attempt to leave the island on the ferry boat they came in on. Janet witnesses her sister actually take a bite out of the horse, and rushes to tell Crockett's group the news, but she gets shot in the head by her father with his remaining bullet after mistaking her for her undead sister. He succumbs to his wounds soon after.
The three survivors, Crockett, Boy and Tomboy, though tempted to stick around on Plum Island, refuse to become like the Muldoon/O'Flynn families, and leave the island on the ferry they came in on. Also of note: the armored truck they rode into the dock earlier in the film contains a million dollars in cash as they plan to use somehow in the future.
Meanwhile, on Plum Island, zombies are seen eating the horse Jane started to eat as all of the remaining human population is killed and eaten by the zombies. In the final scene, the zombified Patrick and Muldoon come up on a hill together, guns in hand, attempting to kill one another once more as zombies. However, it is unknown to them that their guns are empty.
- Alan Van Sprang as Sarge Nicotine Crockett
- Kenneth Welsh as Patrick O'Flynn
- Kathleen Munroe as Janet/Jane O'Flynn
- Devon Bostick as Boy
- Richard Fitzpatrick as Seamus Muldoon
- Athena Karkanis as Tomboy
- Stefano DiMatteo as Francisco
- Joris Jarsky as Chuck
- Eric Woolfe as Kenny
- Julian Richings as James
- Wayne Robson as Tawdry
- Joshua Peace as DJ
- Hardee T. Lineham as Lieutenant Vaughn
- Dru Viergever as Soldier Zombie
- Shawn Roberts as Tony