The film opens where its predecessor, Phantasm III: Lord of the Dead (1994), left off. Mike flees from Boulton mortuary in the hearse, while Reggie is trapped inside by The Tall Man's spheres. Rather than kill Reggie, The Tall Man lets him go, saying he is doing so "to play one last game", then The Tall Man leaves Boulton.
Mike's brother Jody, now a steel sphere who can occasionally resume his human form, contacts and persuades Reggie to search for Mike. On the way, Reggie survives a demon attack and rescues a woman, "Jennifer", from a car accident. They stay the night at an abandoned motel where Reggie tells her the story of The Tall Man. Jennifer is not who she seems to be. She attacks Reggie with two spheres, hidden in her breasts. Reggie vanquishes Jennifer with the use of his sledgehammer and tuning fork.
Mike, tries to uncover the mysteries of The Tall Man in order to escape his transformation. He drives, in his getaway hearse, through abandoned areas, recalling the last days of his youth before The Tall Man's arrival, and ends up in Death Valley. He writes a last testament, in which he expresses his intent to force The Tall Man into a "final" confrontation. As the Tall Man interrupts his attempted suicide, Mike passes through a gateway. He meets a kind man, named Jebediah Morningside. The man tries to speak to Mike, who is frightened away, because Jebediah appears to be the Tall Man.
Back in Death Valley, Mike realizes that he can move rocks with the power of his mind. Jody appears, but a distrustful Mike accuses his brother of having abandoned him. After defending his behavior, Jody disappears. Mike begins working on the hearse's engine, seemingly using parts to build a makeshift sphere. Theorizing that Jebediah must somehow become The Tall Man after traveling through the space gate, Mike plans to prevent Jebediah's first journey. Mike goes through a gate, but finds himself in a deserted city and escapes The Tall Man only with Jody's help.
Meanwhile, Reggie arrives at Death Valley and fights off a group of zombie dwarves shortly before Mike and Jody reappear through a gate. Mike embraces Reggie and tells him not to trust Jody. Taking the tuning fork from Reggie, Mike and Jody pass through the gate and appear in Jebediah's house. Invisible to the old man, they witness how he perfects his craft and approaches the inter-dimensional gate. Mike unsuccessfully tries to stab Jebediah, who vanishes and moments later is replaced by the evil Tall Man who emerges in his place. The Tall Man can see Jody and Mike, forcing Mike to escape through the gate.
Jody finds Mike in a cemetery and attacks him. Awakening on a mortuary slab, Mike uses the tuning fork to immobilize Jody and the Tall Man as they attempt to saw his head open. He kills Jody with the sphere he built. The Tall Man quickly revives and telekinetically takes the fork from Mike. Again, Mike escapes through the gate back to Death Valley, this time pursued by his nemesis.
Reggie tries to shoot but is overpowered by The Tall Man. Mike then summons the sphere he built and uses it to impale The Tall Man in the neck. Amused by what he calls Mike's "toy", The Tall Man is momentarily distracted. At this moment, Mike activates the hearse's motor, which turns out to be the true weapon, a strange inter-dimensional bomb, against the Tall Man. The Tall Man is once again supposedly vanquished after the explosion consumes both him and the car. However, a new Tall Man immediately comes through the gate, revealing that The Tall Man is but one of many. Resuming the surgery started by his predecessor, The Tall Man removes the golden sphere from Mike's head and then passes through the gate.
Reggie arms himself and chases after The Tall Man through the gate. Close to death, Mike recalls a childhood memory of him climbing into Reggie's ice cream truck as they both drive off into the dark night.Angus Scrimm as The Tall Man
A. Michael Baldwin as Mike Pearson
Reggie Bannister as Reggie
Bill Thornbury as Jody Pearson
Bob Ivy as Demon Trooper
Heidi Marnhout as Jennifer
Production and sequel
Canadian filmmaker Roger Avary, a self-professed hardcore fan of the Phantasm series, wrote an epic screenplay titled "Phantasm 1999 A.D." as a sequel to Phantasm III: Lord of the Dead. It was set in a post-apocalyptic near future and would feature Bruce Campbell as a co-star. As the project ran into financing difficulties, Don Coscarelli wrote and directed this fourth installment as a precursor to the project, using numerous outtakes from the preceding films. Avary also appeared in the film as one of the Civil War soldiers. Despite these efforts, the budget for the sequel, now retitled Phantasm's End, could not be secured.
Oblivion's budget was considerably lower than the previous two Phantasm films. While Phantasm II had a budget of $3,000,000 and Phantasm III: Lord of the Dead had a budget of $2,500,000, the filmmakers were only able to secure $650,000 to make Phantasm IV: Oblivion. The filmmakers had to be inventive with the budget, much like the first film, which had only $300,000 budget. For the Civil War dream sequence a Civil War reenactment group was hired in exchange for a $200 donation. Because the production could afford to build only a few sets, several key scenes were filmed in the desert, making this the only Phantasm movie without significant scenes inside a mausoleum setting, except the very beginning. The swarm of spheres was done by several fans of Phantasm, who then showed it to Bannister who, in turn, showed it to Coscarelli. KNB EFX group also helped out a bit on the film as a favor to Coscarelli.
Rumors of a sequel were reignited in June 2007 by footage contained in Don Coscarelli's Farewell to The Alamo Drafthouse, featuring Angus Scrimm and A. Michael Baldwin in their roles. However, in an interview with Reggie Bannister that surfaced on YouTube, Bannister stated there was no activity or development involving a fifth installment but that anything was possible in the future.
On March 25, 2014, it was announced that a fifth installment in the series, Phantasm: Ravager, had been filmed secretly. The film was released on October 7, 2016.
The film was released on Video in 1998 and on DVD in 2000, both by MGM Home Entertainment. In 2008, Anchor Bay Entertainment released a special edition of the film. News reports said it would be the uncut version, however, the special edition contains only the R-rated version (as did the MGM release).