In Burundi, a British forensic anthropologist is examining the corpses in a mass grave, claiming they were all killed in an identical manner. When the woman digs her shovel into what she believes is another grave, an unseen creature attacks, and violently drags her into the river. The UN soldiers accompanying her fire into the water, but only her partially devoured corpse floats to the surface, before being devoured.
In a New York City newsroom, television journalist Tim Manfrey (Dominic Purcell) is assigned by his boss, Roger (Patrick Lyster), to travel to Burundi with Aviva Masters (Brooke Langton), a reporter who deals with animal stories and has become interested in Gustave, a gigantic, fierce crocodile known to have killed hundreds of people in Africa, over the years. With the killing of the anthropologist, Gustave is suddenly a story of interest to the world. Tim doesn't want to go, knowing that Burundi is a war zone, but he has little choice, since one of his stories turns out to have been based on falsified evidence. Tim and Aviva are accompanied to Burundi by Tim's cameraman and friend, Steven Johnson (Orlando Jones) and herpetologist Matt Collins (Gideon Emery), who is intent on capturing Gustave alive.
At the airport in Bujumbura they are met by a government official nicknamed Harry (Dumisani Mbebe), who tries to delay their departure by warning them of unrest in the bush, caused by a dangerous warlord who has nicknamed himself "Little Gustave." Tim manages to overrule Harry by faking a call to Roger, and the team departs the next day, accompanied by two soldiers. When the party reach the village where the last attack occurred, they meet their guide, a licensed hunter named Jacob (Jürgen Prochnow), and are blessed by the local shaman. The friendly villagers later, assemble a steel cage in order to capture the crocodile and take it to a nearby swamp. The first attempt to capture Gustave, by placing a goat as bait fails, but Matt manages to shoot a tracking dart on it.
In the next attempt, Jojo (Gabriel Malema), a teenage villager who helped set up the cage, uses himself as live bait to capture Gustave. The beast arrives, and tries to devour him, but disappears, as Tim, Matt, and Steven race to rescue him. Meanwhile, Avivia catches one of the soldier escorts stealing money from a tent. The soldier knocks her down, but Gustave arrives and kills him. Avivia escapes unharmed, and catches up with the others. The remaining guard relays over his radio that the Americans videotaped the shaman's execution. Just as the group realizes that the soldiers work for Little Gustave, the remaining guards, believing Jacob videotaped the evidence, wounds him; Jojo intervenes, and shoots them. While Jacob's wound is being treated, Gustave attacks the group. Jacob recalls the story of how his wife, Ona, was killed by Gustave, and that he swore revenge. Jacob produces a grenade, and detonates it as Gustave grabs him in his jaws, and devours him, but the explosion fails to kill the crocodile.
The next day, a helicopter arrives to airlift the survivors, but a truck arrives with two of Little Gustave's men, who fire a rocket at the helicopter. The group ducks, except for Matt, who runs after the helicopter to stop it from flying away. Matt is rammed by the truck and shot to death by the younger of the two militias, a teenager performing what is clearly his first execution. When the driver of the truck notices the rest of the group, Tim yells for them to split up. In the ensuing chase, both of Little Gustave's men are killed: when the truck crashes into the river, the teenager is thrown out and dies on impact, while the driver is shot by Aviva when he tries to strangle Tim to death.
Steven stumbles upon Gustave and struggles to escape. While Aviva stays with the injured Jojo, Tim goes to look for Steven, but finds only his camera. As they are waiting for help, Tim remarks to Aviva that he now understands the shaman's earlier words that "we make our own monsters." Matt had earlier told the group that crocodiles frequently feed on carrion, and there is no limit to how large they can grow, given enough sustenance; it is the bodies from the civil war, floating in the river, that have given Gustave a taste for human flesh, and allowed him to reach such a gargantuan size, as the years go by.
Harry arrives in a Range Rover, but Tim realizes that he is Little Gustave and wants the video evidence. Tim attempts to trick Harry by giving him the GPS tracker linked to the dart on Gustave, saying it will locate the computer with the video. Harry forces Tim and Aviva to lead them to the "computer." While Harry holds Aviva at gunpoint, Tim and one of Harry's men follow the tracking signal to Gustave's lair, where the crocodile is sleeping. Tim finds Steven's mutilated body, and a combat knife in the scattered human remains, and stabs the guard. At the same moment, Aviva splatters Harry with Matt's container of crocodile pheromones and runs. Gustave wakes up and ignores Tim and Aviva in favor of devouring Harry.
Tim, Jojo and Aviva climb into the Range Rover, but Gustave attacks through the rear window. Tim stabs the crocodile in the mouth with a machete. It then roars in defeat, as the others manage to escape. Tim, Aviva, Jojo and Wiley receive medical treatment and fly back home to America, watching leftover footage of Steven on his camera. The end credits state that the Burundian Civil War ended with a ceasefire in 2005, but Gustave is very much alive and still killing people in the rivers of Burundi.Dominic Purcell as Tim Manfrey
Brooke Langton as Aviva Masters
Orlando Jones as Steven Johnson
Jürgen Prochnow as Jacob Krieg
Gideon Emery as Matt Collins
Gabriel Malema as Jojo
Dumisani Mbebe as Harry / Little Gustave
Patrick Lyster as Roger Sharpe
Linda Mpondo as Gold Tooth
Ernest Ndhlovu as Shaman
Thandi Nugbani as Shaman's wife
Kgmotoso Motlosi as Shaman's son
Walter Emanuel Jones as Voice
Filming commenced in April 2006 in South Africa. Another crocodile horror film, Rogue, had to be pushed back until Fall 2007 because of the film's similarities with Primeval.
The film's promotional trailer dubs Gustave a "serial killer", who has claimed more than 300 victims and "remains at large". It is compared to Jack the Ripper and the Zodiac Killer with his non-human status never mentioned except for a brief line where the narrator says, "He's real, but he's not human". A shortened version of this trailer does not contain this at all. However, in the trailer, a crocodile, presumably Gustave, briefly flashes on screen. The promotional poster similarly calls Gustave "the most prolific serial killer in history". The film's official website rarely makes any mention that the killer is in fact a crocodile.
The film was poorly received, gaining a 19% rating on Rotten Tomatoes. Naturalist Patrice Faye said Primeval "is an insult to purists and herpetologists but, above all, an insult to Burundi. It shows the country in a bad light, and the people of Burundi are made out to be savages, barbarians, thieves, and murderers".