An edited version of the film aired on the SciFi Channel on October 15, 2005. The R-rated version of the film was released on DVD on April 18, 2006. The film was originally advertised as Return of the Living Dead 4: Necropolis but once it was finally released, the number 4 was removed from the title.
Both Necropolis and Return of the Living Dead: Rave from the Grave are criticized for straying away from the series' rules. Most notable of these changes is that Trioxin zombies are no longer the indestructible juggernauts of the first movie, but instead much weaker than even "Romero zombies." Several times throughout the movie, they are seen to be dispatched with no more than a few body shots, sometimes as few as two hits will end their undead life. Prior to this film, nothing short of incineration or electrocution with extreme high voltage would destroy a Trioxin zombie. However, this may be a different form of Trioxin; here, it's referred to as "Trioxin 5," which may explain why the zombies are weaker.
Set 10 years after Return of the Living Dead 3, the film starts out with Charles Garrison (Coyote) traveling to Chernobyl to collect the last 6 canisters of Trioxin 5. Two Russian sellers take him to an empty power station which contains the Trioxin. One of the Russians get Trioxin on his hands, turning him into a zombie. Upon hearing screams, Garrison runs to see the zombie eating the other Russian partner. Garrison promptly shoots the zombie in the head.
It is then revealed that the parents of Julian and Jake "Pyro" Garrison (the nephews of Charles) were volunteers who died a year earlier at Hybra Tech. Julian leaves the house to go motor biking with his friends. During a stunt, one of Julian’s friends, Zeke falls and gets knocked unconscious. At the hospital, a doctor tells Julian that Zeke had an unexplained reaction to the painkillers and is pronounced dead on arrival.
One of Julian’s friends, Katie, works at Hybra Tech and notices Zeke being brought in. Julian and his friends manage to hack their way into Hybra Tech website and discover Zeke is to be used as a test subject and decide to rescue him.
Meanwhile, Charles is experimenting with the Trioxin. He manages to reanimate an arm and a corpse. However, some of the gas manages to escape through the pipes (unexplainably not affecting Charles) and reanimates a dead rat that two homeless men were eating and it proceeds to attack them.
By using fake IDs, Julian and his friends manage to get into Hybra Tech, with Katie at the security center giving them advice over walkie-talkies. They end up sneaking through the ventilation shaft and find out that Pyro had followed them. They get out of the vent and find themselves in an armory. After some searching they are found by Charles, who shows them where Zeke is.
The group discovers a room full of zombie clones. Uncle Charles explains that they are to be the new test subjects. He also reveals that Julian’s parents are alive before managing to escape. Katie tries to deactivate an alarm, but in the process releases all the zombies in the complex. During the chaos, Zeke is bitten on the neck by a zombie, and the group manages to make it to the armory and escape into the vents. Julian, Carlos and Cody separate from the group to find Julian’s parents, however Carlos is bitten shortly after entering the building.
Zeke, Becky and Pyro manage to make it to the parking lot and are able to find keys to a jeep. Zeke begins to behave abnormality,Without Becky or Pyro noticing that Zeke's eye color has change to a pale gray. Unfortunately, Zeke turns into a zombie and tries to eat them, causing them to crash. Julian meanwhile has found the building where his parents are being held. He finds his zombie parents in a holding tank and sees they have been suited up with circular saws and miniguns to become “uber-soldiers.” They leave the room in disgust and after being chased by zombies run to the roof. A few minutes later Uncle Charles appears in the room with Julian’s parents and releases them from their tanks.
Julian manages to abseil down the building from the roof. At the bottom, he encounters two zombies. The zombies are killed as Katie appears in a new truck and runs the zombies over. Julian and Cody get in the truck.
Meanwhile, Pyro and Becky are trying to fend off zombies. Zeke runs towards Becky before she is pushed out the way by Pyro. Zeke then eats Pyro’s brains. Becky manages to scare Zeke off just before Katie arrives in the truck. They pick up Becky and escape the zombies. As they drive, Julian’s dad appears and shoots the truck with the mini-gun. After he has finished shooting, Becky gets out the truck and throws a grenade at him, nearly destroying him.
They all get out of the truck and start running, but encounter Zeke and Julian’s mother. Zeke starts a fist fight with Julian, whilst the group attempt to destroy Julian’s mother. They succeed while Julian manages to destroy Zeke with a grenade that was attached to him, when Julian pulls the clip.
The SWAT team arrives and shoots the remaining zombies, including Julian’s dad, who began shooting moments after the police arrived. He shoots Katie before the SWAT team is able to kill him. The film ends with the SWAT team disposing of the bodies, and Uncle Charles escaping with the barrels of Trioxin 5. The closing scene of the movie shows a newscaster reporting about a supposed zombie outbreak which Hybra Tech denies. In the end the newscaster is attacked by a zombie as the screen goes black.