In Kuwait, a military unit uncovers an American helicopter downed by friendly fire at least three years ago. As the wreckage is inspected, Master Sergeant Sam Harper (David "Shark" Fralick), one of the burnt bodies within, springs to life, kills a sergeant and a major (William Smith), and returns to an inert state after muttering, "Don't be afraid, it's only friendly fire!"Several weeks later, Sam's body is delivered to his hometown of Twin Rivers, which is preparing for the annual July 4th Independence Day festival. Sam's wife Louise (Anne Tremko) is given custody of the casket containing Sam's remains, which are left in the home of Sam's estranged sister Sally (Leslie Neale), who lives with her patriotic young son, Jody (Christopher Ogden). Sam reanimates in the early hours of the Fourth of July, and proceeds to kill and steal the costume of a perverted Uncle Sam named Willie (Mark Chadwick), who spies on young women undressing in their bedrooms. Sam then makes his way to a cemetery, where he murders two of three juvenile delinquents who had vandalized tombstones, and desecrated an American flag.During the Independence Day celebration, which a corrupt congressman (Robert Forster) is visiting, Sam beheads the third delinquent (who also deliberately botched his performance of the National Anthem at the start of the festival), kills Jody's teacher (who had opposed the Vietnam War) with a hatchet, shoots Sally's unscrupulous lawyer boyfriend in the head, and kills a teenage girl (who was caught earlier smoking marijuana) running the BBQ stand by burning her face on the grill after she discovers the severed head of the third delinquent on said grill. Despite these deaths, the festivities continue, but are thrown into disarray when Sam uses the fireworks gear to blow up the congressman, and a flagpole to impale Louise's deputy boyfriend, who tried but failed to rescue the congressman. As this occurs and the various attendees flee, Jody is told by his mother and aunt that his supposedly heroic idol Sam was in fact an alcoholic psychopath who physically and sexually abused them, and only joined the military so he could get a "free pass" to kill people.Jody is told by Barry, another boy who has established an unexplained mental link with Sam, that the undead Sam is responsible for the deaths. With help from Sam's old mentor Jed (Isaac Hayes), the boys go to Jody's house, where they find the lecherous sergeant (Bo Hopkins) who had dropped Sam off dead, and stuffed inside Sam's coffin. Realizing that Sam will probably go after Louise, the boys and Jed go to her home, where Sam blames Jed (who had told him tales of how glorious combat was) for his current state. Jed retorts by yelling, "You never fought for your country! You just killed for the love of killing!"Jed's gun proves ineffective against the undead Sam, so he and Louise go to get Jed's cannon while Jody (who Sam claims is the reason he came back) keeps Sam occupied. Jody lures Sam outside, and Jed blasts him with the cannon, destroying him, and Louise's house. The next day, Sally watches as Jody burns all of his war-themed toys.