The expansion takes place in two time periods. The first is roughly five hundred years before the events in Aliens versus Predator 2. The second time period is in 2230, about five weeks before the beginning of the Alien's game in Aliens versus Predator 2.
In both time periods, the game takes place on the planet LV-1201, the site of Aliens versus Predator 2. The expansion revisits the Forward Observation Pods, a group of elevated habitation modules which comprise one of two main human facilities on the planet. Specifically, the player visits Pod 5, which was destroyed prior to the events in Aliens versus Predator 2. The cause of its destruction is revealed in the expansion. The player also visits Zeta Site, a portion of a Xenomorph Hive alluded to in the main game. Zeta Site contains Engineer technology and Yautja ruins.
- The Predalien is the primary Xenomorph playable character. The Predalien starts life as a Facehugger which assaults a Yautja as it enters stasis. The creature birthed from his chest five hundred years later in the human-built Pods, just after the Predator sent a message.
- Major Dunya is the human playable character, a member of the Iron Bears, a private military contractor employed by the Weyland-Yutani Corporation to maintain security on LV-1201. She also plays a small but important role in Aliens versus Predator 2 as a non-playable character. She is engaged to Dimitri, a fellow Iron Bear.
- The Ancient Predator is the main Yautja character. He was the first of his species have a Hunt on LV-1201. He discovered a Hive of Xenomorphs there, and his clan quickly built a facility among the Hive from which to organize their Hunts. When the Hive facility was breached, he was accidentally put into stasis while in the process of restoring the stasis fields in the Egg chambers.
- General Vassili Rykov is the leader of the Iron Bears, who runs an operation smuggling Pilot technology off-planet behind the facility administrator's back. He sends Dunya on a mission to retrieve one such piece of technology at the beginning of her campaign. He plays a crucial role in Aliens versus Predator 2; he is the final enemy faced by the Predator Prince.
- Dimitri is Dunya's fiance, who is endangered by Xenomorphs in the expansion. He appears briefly in Aliens versus Predator 2 before he is killed by Xenomorphs. His death gives Dunya part of her motive for her actions in that game.
- Popov is another henchman. He is killed by Aliens while escorting a Predator Artifact through the Pods.
- Serge is a Russian Iron Bear. He is killed by Aliens while retrieving the Artifact.
- Becker is an Iron Bear. A Texan, he does not agree with some of Rykov's tactics. He is killed by Aliens when retrieving the Artifact.
- Dr. Arnaud Eisenberg is the head researcher in charge of the LV-1201 facility. He appears in the ending of the game inside Gateway Station.
- Winter is a guard in Pod 5, who was killed by the Predalien.
- Jerry is a Pod 5 guard who was crushed by a sign while smoking. The sign itself reads "No Smoking". A punishment at a right time. The sign might be part of the hatch that the Ancient Predator blew off, allowing him into the pods.
- Dr. Adam Post is a scientist that guides Dunya in the first level. He was studying the relics in the Zeta site.
The Predalien begins the game as a Facehugger inside the Predators' hunting camp on LV-1201, five hundred years before the events of the main game. When the camp's integrity is breached, the Facehugger sneaks through the complex, seeking a solitary host to impregnate. The Facehugger scurries through vents and under floor grating, using occasional Xenomorph attacks as diversions. Finally, it locates a lone Ancient Predator attempting to repair a stasis field generator below the facility. It strikes, but both creatures are caught in the reactivated stasis field.
Five hundred years later, the Predalien finally emerges from its host inside Pod 5 at the Weyland-Yutani research facility established on LV-1201. Now a Chestburster, it quickly finds a food source while evading human guards. It makes its way through vents, corridors and a lavatory to the Pods' morgue, where it feeds and molts into an adult.
When fully-grown, the Predalien stalks and slaughters its way through Pod 5, seeking the Artifact that its host was carrying. Its path back to its host is now blocked by wreckage from the humans' battles with other Xenomorphs, so the Predalien must find an alternate route. It cuts through the botanical labs and nears the Artifact when alarms sound — the Pod's supports are going to be demolished by explosive, thereby destroying the Pod and hopefully wiping out the Xenomorph outbreak. The Predalien abandons its pursuit of the Artifact in order to save its own life, fighting its way through a small army of combat synthetics and armored Exosuits, finally escaping through a vent near the pod's generator. It flees with several other Xenomorphs along a support girder just before the supports are destroyed and the Pod collapses.
Major Dunya's game begins five weeks before the incident in the main game. She is spending some quality time with her fiancé Dimitri when they are interrupted by a call from their superior officer, General Rykov. Rykov asks to meet with Dunya immediately, explaining that they have "found a buyer". When they meet, Rykov explains that Dunya is to retrieve an Artifact discovered during a synthetic team's exploration of Zeta Site. The synthetics were quickly destroyed, but they transmitted information about the Artifact back to Rykov. Dr. Post, a scientist in Rykov's employ, provides Dunya with a "worm device", designed to hack into Engineer technology and shut down systems indiscriminately so that she can retrieve the Artifact.
Dunya, along with two other Iron Bear mercenaries named Serge and Decker, infiltrate Zeta Site while the Weyland-Yutani guards have been conveniently incapacitated. They descend to the Hive, but are overwhelmed by Xenomorphs, with only Dunya suyrviving. She flees through the Hive, scavenging supplies from the destroyed synthetic expedition, and makes it to the Artifact chamber. Suddenly, the Xenomorphs pursuing her stop dead in their tracks, watching warily. Dunya reports the situation back to Rykov, then installs the worm device. After some time, the Engineer technology around her starts to fail and collapse, blocking her exit route.
Finally, the Artifact itself shuts down, allowing Dunya to retrieve it. She does so and is immediately accosted by Xenomorphs. She escapes by clambering over the ruins to the abandoned Predator hunting camp. She fights her way through dozens of Xenomorphs and cunningly-placed Eggs to the surface, then across a series of narrow, bridge-like formations spanning a series of rocky hills. She finally reaches a waiting APC, which takes her back to the Pods.
Later, at the Pods, Rykov informs Dunya that Xenomorphs have infiltrated the Pod and orders Dunya to retrieve the Artifact from storage. Dunya goes to secure the Artifact, arriving just in time to see the Ancient Predator making off with it. Rykov, having encountered Predators before, warns her to abandon the Artifact and evacuate the Pod. She arrives at the main elevator, but learns that Dimitri went to seal the breach that allowed the Xenomorphs entry, and he has not been heard from since. Dunya tells the others to evacuate the Pod, insisting that she will keep the cargo area clear until her fiancé returns. Using a mounted minigun and a few automated sentries, she holds the line until Dimitri rejoins her. They both escape in a lift, and Rykov detonates the supports keeping Pod 5 attached to the rest of the facility. Pod 5 crashes to the valley floor below.
Roughly five hundred years before the events of the main game, a Predator spacecraft encounters the planet LV-1201 and finds it to be teeming with life. A lone Ancient Predator is sent out to explore and hunt game, and he encounters a verdant world, full of dangerous prey including carnivorous, moose-like creatures (Buhlagh), hulking, bipedal reptiles capable of disguising themselves as part of the terrain (Chameleons) and wormlike organisms that attack from underground (Tentacles). Quickly, however, the Ancient Predator discovers far more dangerous prey: Xenomorphs. The Predator follows them to their Hive, through ancient Engineer ruins, where he discovers and activates an ancient Artifact that has the power to keep Xenomorphs at bay.
Eight months later, the Predators have built a hunting base camp around the Artifact from which they launch hunts deeper into the Hive. The Ancient Predator descends, with some clan mates, deeper into the Hive, in search of the Xenomorph Queen. However, an alarm from the facility cuts their Hunt short. The Predators return to the facility to find it overrun by Xenomorphs; the Artifact has been powered down, allowing them access. The Ancient Predator fights through hordes of Xenomorphs, restores power to the Artifact, and then attempts to restore power to stasis fields constructed by the Engineers to keep bays of Xenomorph Eggs from hatching. While manually repairing one field generator, the Ancient Predator is attacked by a Facehugger and both are trapped in the newly-activated field.
The Ancient Predator awakens five hundred years later when the field is deactivated. He recovers his Bio-Mask and makes his way to the now-ruined Artifact chamber, where he sees Dunya steal the Artifact. The Predator pursues her through the infested ruins of the Predator camp, finally tracking her to the Pods. He infiltrates Pod 5, inadvertently allowing hundreds of Xenomorphs to gain access with him, before hacking into the human systems to learn the location of the Artifact, which he retrieves. He then breaks into a communications room and transmits a signal to his fellow Predators in the Nodus Secundus system, nine weeks away. As the Ancient Predator laughs in celebration of its success, the Chestburster incubating inside him bursts from his ribcage, killing him. However, the transmission he sent is detected by Prince and his clan, and they prepare for their own hunt on LV-1201.
Primal Hunt was released to extend Aliens versus Predator 2 (developed by Third Law Entertainment). The pack included several new weapons (dual pistols and sentry guns for human players; energy flechette for Predator players), new indigenous wildlife and new multiplayer maps. Its single player campaign also tied up several loose ends in the story of Aliens versus Predator 2 (including the identity and nature of the Artifact sought by the corporates in Aliens versus Predator 2). However, factors such as the shortness of the single player campaign, and the sometimes clumsy nature of the pack's additions limited its appeal.
As with the main game, the expansion packs' three stories are interwoven, although they take place across two vastly different time periods. In fact, the level of interaction is even greater than in the base game, with the Alien character actually being spawned from the playable Predator character. Notable examples include:
- The Predalien (in Facehugger form) attacks the Ancient Predator and impregnates him with a Chestburster.
- The Ancient Predator pursues Dunya after she retrieves the Artifact from the ruins of the Predator camp.
- Dunya later sees the Ancient Predator reclaim the Artifact for himself.
- The Predalien emerges from the Ancient Predator. This incident marks the only time a playable character in the video game series is killed by another playable character.
Primal Hunt also reveals that it is the Ancient Predator's transmission that lures Prince and his clan mates to LV-1201 in the main game. The destruction of Pod 5 is also mentioned in the base game.
- The first two levels of the Predator Campaign (Hunt and Stasis), along with the first level of the Predalien's Campaign (New Hosts), occur five-hundred years before the events of Aliens versus Predator 2. As such, the year would be 1730 by human standards.
- Although Dr. Post first appears in this game, a doctor Adam Post was mentioned in text logs in the main game. It is highly likely they are one and the same, as the notes in the main game mention that he is studying Zeta Site's relics.
- The Hacking Tool was removed from the expansion pack, as the human character (being a member of the Iron Bears) has no need to use it.