Los Angeles, 1997. The temperature in the city stands in the high 90s. In the streets, the LAPD and Colombian gangsters are fighting a pitched battle that the police are rapidly losing. Efforts to rescue two wounded cops have failed and backup is unavailable. Lieutenant Mike Harrigan bursts onto the scene. Harrigan arms himself and drives his car directly at the front lines, giving his comrades the chance to save their wounded friends. The Colombians seize the chance and retreat into a nearby building that serves as their stronghold.
While the Colombians arm themselves they are attacked by an invisible enemy and slaughtered. Only the gang's leader, El Scorpio, makes it out, shooting wildly at Harrigan and his team. The hysterically terrified El Scorpio escapes to the roof, with Harrigan behind. On the roof, El Scorpio spots a distorted human figure and raises his guns to shoot. Harrigan shoots the man, who falls off the roof and is killed.
In the room where the gangsters were arming themselves, Danny notices that one of them has been stripped naked and hung upside down about 40 feet above the floor. Marveling at the strength needed to perform such a task, Danny turns away and the body is pulled up by unseen hands. Outside the building, Harrigan is met by his captain, Heinemann, and told that he disobeyed direct orders. Harrigan argues with him, citing the war they're fighting an losing in the streets to better armed Colombian drug dealers who also have greater numbers. Adding to the mayhem is another faction, Jamaican gangsters, who are also fighting the cops and use brutal terrorist acts against their Colombian enemies.
Back at his precinct, Harrigan is lectured by his other captain, who informs him that a federal investigation, lead by a man named Peter Keyes, is not to be interfered with. Keyes claims that his team is trying to stop the Colombian and Jamaican gangs from establishing an empire on the west coast. Harrigan agrees not to interfere in Keyes' work. Harrigan also welcomes a new member to his team, Jerry, a smart-mouthed and cocky detective.
In a luxury apartment, Ramon Vega, the leader of the Colombian gangs is having sex with his girlfriend when they're interrupted by Jamaican gangsters. They hang him upside-down and cut his heart out as part of a voodoo ritual. They are suddenly attacked by an invisible enemy using superior weaponry. All of them are viciously slaughtered. When Harrigan and his crew arrive on the scene they enter the apartment against orders and find several bodies hung from the ceiling, skinned. Vega's girlfriend is the only survivor. Keyes enters the room and orders them all out. His own crew begins to examine the room, using unusual gadgets. Also in the room is a sleazy reporter, Tony Pope, who films much of the carnage. Everyone is ejected from the room and the woman who survived is taken away in an ambulance.
Danny and Harrigan agree to meet at the scene later that night and conduct their own investigation. Danny arrives first and looks around the room. Seeing what appears to be a trail of claw-marks leading up a decorated column, he climbs up. In the rafters, he spots a small object embedded in an air-conditioner. He pulls it loose and examines it; it appears to be a spear-tip of some sort. Suddenly, he hears Harrigan's voice nearby and loses his footing and falls. An arm catches him and Danny looks up to see a large figure holding him by the ankle. The figure drags him back up and kills him. As he dies, Danny's necklace falls to the floor and is splattered with his own blood.
Harrigan finds himself in Captain Heinemann's office. The captain reprimands him harshly for Danny's death and continuing to interfere with Keyes' investigation. Harrigan leaves the meeting angry and confronts Keyes in the station's lobby, telling him that he's motivated by revenge and will find Danny's killer himself. Strangely unoffended, Keyes tells him that the magnitude of the situation is beyond his comprehension. At the police forensics lab, Harrigan has a doctor examine the spear tip he recovered from Danny's body. The doctor determines that the metal isn't found on the Periodic Table of Elements. She also tells Harrigan about how Danny was murdered: by a sharp-edged weapon that cleaved Danny's heart.
Harrigan tells Danny's wife, Leona, to arrange a meeting with King Willy, the leader of the Jamaican gangs, with the intention of sharing information about their mutual nemesis. Harrigan also meets with Jerry, who has done some surveillance on Keyes. The survivor of the attack in Vega's apartment was taken away in a helicopter and Jerry has been unable to find her. As he and Harrigan leave the bar, they are met by a large limo filled with Jamaican gangsters. Harrigan joins them and is taken to an alley where he meets King Willy. Willy, a voodoo practitioner, mysteriously tells Harrigan that the enemy they both face comes from a netherworld he can't understand. Harrigan leaves without answers. Just after he goes, the predator jumps to the ground behind Willy and walks through a small pool of water. The water causes an electrical disturbance on the predator's body and it becomes visible. It challenges Willy to blade combat and Willy loses. The predator carries Willy's severed head away and is seen cleaning the tissue off the skull for a trophy.
Harrigan calls Jerry and Leona at the forensics lab. The doctor tells them that the only lead she has is from evidence collected at the scene of Danny's killing: whomever killed him left traces of debris that came from a slaughterhouse. Harrigan and Jerry recall that Jerry had lost track of Keyes in LA's meatpacking district. Harrigan tells them to meet him there.
Harrigan goes to the cemetery to pay his respects to Danny. While he's there, he sees Danny's necklace hanging from a tree limb. Startled, Harrigan, looking around for his enemy, grabs the necklace and realizes the predator is stalking him specifically. Moments before, a small boy plays in the cemetery with a toy gun. The predator targets the boy but does not kill him when it realizes the boy poses no threat because he's unarmed.
On the subway to the slaughterhouse district, Jerry and Leona encounter a group of gang members harassing a passenger. The passenger pulls a gun on them and the gang members do the same, prompting several other commuters to pull their guns as well. As Jerry and Leona try to defuse an impending slaughter, the predator jumps onto the roof of their car and enters it. It wades through the passengers, killing anyone who possesses a weapon. Leona is able lead most of the passengers out of the car and to the opposite end of the train. While she does, she sees Jerry shooting at an invisible target. Jerry's bullets have no effect and he leaps at the predator with a large knife. Leona pulls an alarm that stops the train and she guides the passengers out of the platform. She walks back to the last car and finds Jerry and a couple of commuters hung upside and dead. The predator suddenly appears and grabs her. Looking her over with it's infrared vision, it sees that she's pregnant.
Harrigan arrives on the scene and sees the carnage. Jerry's body is gone and he walks down the tunnel, searching. He spots the predator ripping Jerry's skull and spinal column from his body. Harrigan chases it to street level. He steals a police car and chases it several blocks until he's stopped by Keyes' men. Taken to a high-tech command center, Keyes explains that the predator is an alien that uses advanced weaponry. He tells Harrigan about a commando team that encountered another of these creatures in a Latin American jungle 10 years prior. Keyes says that they believe the alien can only track it's prey using infrared technology and that his team, intending to capture it and study it, will wear special suits that will insulate their body heat and make them invisible. At the same time, they will dust the slaughterhouse with radioactive particles that will make the alien visible. Their ultimate goal is to freeze the alien with frozen nitrogen. The predator comes to the location every couple of days to eat the beef there. Keyes tells Harrigan to stay in the command center and observe.
Keyes and his team move into the slaughterhouse. Their equipment functions well at first, until a couple of team members step on a creaking stair. The predator, hearing the noise, uses a small control panel to adjust it's vision enhancer, which changes several times until it's able to see the beams from the lights the team are using. Harrigan tries to warn Keyes that they've been spotted but the team is attacked by the predator, which kills nearly all of them. One of the teams sprays a smoke detector with nitrogen, setting off the warehouse's sprinkler system. Harrigan leaves the command center, arms himself and blows down the door just as the predator fires a blast from it's laser cannon at Keyes. Harrigan shoots at the predator, damaging its laser cannon. The alien tries to activate it's cloaking system but the water falling from the ceiling prevents from becoming invisible. Harrigan shoots the predator several times with a shotgun, blowing it onto its back. He approaches it slowly and removes it's helmet, studying it briefly before it wakes up suddenly and throws Harrigan backwards. The predator finally corners Harrigan and is about to kill him when Keyes intervenes, trying to blast the monster back with frozen nitrogen. Keyes tells Harrigan to retreat just as the alien throws a smart disk, cutting Keyes in half. The predator retreats to the roof of the building, using a breathing mask. It throws its large hunting spear at Harrigan and misses. Harrigan uses the spear to push the alien and himself off the building, where they both hang onto a ledge. The predator activates a timer connected to a small nuclear charge. Before the charge can go off, though, Harrigan uses the alien's smart disk to sever it's arm, deactivating the bomb. The alien falls down the side of the building and crashes into an apartment bathroom. It uses an elaborate first aid kit to heal it's wounds and again retreats. Harrigan follows it, falling into a cavern below the building where the alien's spacecraft has been hidden.
Inside the spaceship, Harrigan finds a small shrine of sorts with skulls of humans, animals and aliens. The predator once again attacks Harrigan who fights it off and kills it with its smart disk. After it falls dead, several more predators appear and carry their fallen comrade off. The last one to leave looks over Harrigan briefly and tosses him a flintlock pistol, a trophy from a previous hunt. Engraved on the pistol is the original owner's name and the year 1715. Harrigan hears the ship starting up and runs out to cover just before the blast from the engines fills the cavern. As Harrigan walks out of a tunnel he meets one of Keyes' assistants, who, upon seeing the haggard Harrigan, leaves him.