Set in 2152 (two years before the events of the film), Avatar: The Game starts out with a new signals specialist, named Able Ryder, arriving at Pandora, he/she is assigned to an area called Blue Lagoon, a large piece of jungle, fenced in to make sure no larger predators get inside.
His/Her first mission is to save five marines from Viperwolves, with his/her CO, Kendra Midori, suggesting he/she use a turret to help fend off the wolves. After saving the marines, Ryder must go help another Sig Spec, Dalton, who is afraid of the Viperwolves and trapped outside the fence. Then Ryder gets on a boat, a Gator, to another base, where Ryder is told to go fix the fences and animal repulsors, which are attracting creatures rather than keeping them away. After fixing the fences, Ryder is told to enter his avatar. Ryder's first mission in his avatar body is to get cell samples from certain non-hostile plants. After getting the samples, a Na'vi, Tan Jala, tells Ryder to kill his infected animals. A RDA air strike is then seen being launched on the Na'vi village where Ryder had locked the signal. He finds out that there is a mole and that it is one of the avatar drivers. He must then follow Tan Jala, who will lead him to the mole. After finding who the mole is, a scientist named Rene Harper, who is sympathetic with the Na'vi plight, Ryder sees the Na'vi village destroyed in the air strike previously. Commander Falco and his soldiers arrive via helicopter and try to force Rene into surrender. Harper then tries to persuade Ryder to join the Na'vi and leave the RDA. When Falco hears this, he orders Ryder to shoot Rene Harper and keep his allegiance to the Corporation. Ryder must then make a game-altering decision of siding with the defensive Na'vi or siding with the more offensive, better- armed RDA.
If the player sides with the RDA, Ryder, Commander Falco, and his soldiers corner Rene Harper, and he jumps from a cliff rather than surrender to the RDA. As Rene falls, he shoots Ryder in the chest with a bow and arrow. His avatar is killed, but Ryder's human body survives.
As he returns to base on a Scorpion with Kendra, two banshees attack and force down the helicopter. No one is killed, but the pilot is hurt in the crash. Midori informs Ryder of a base near the Crash Site, and that he could use one of the aircraft. However, when he arrives, he finds the base is under constant attack by banshees, resulting in the destruction of many operational Scorpion and Samson helicopters, and causing many casualties. Ryder enters the control room, and the commander tells him to take a helicopter above and destroy the banshee nests, eradicating the banshee threat. When Ryder returns to retrieve missiles from the Crash Site, he learns that the pilot died from his injuries. He reequips the missiles to the helicopter and completes the task, and the player can see that aerial reinforcements are arriving and battling any remaining banshees in the area.
Ryder is then transported to a combat area known as the FEBA, where Na'vi warriors, under the powerful Beyda'mo(who, ironically, dislikes Ryder, even if he joins the Na'vi), are inflicting death and destruction to the RDA and slowing the advance to a halt.