In a technologically advanced near future, Mills, a cyborg working for Harbinger Corporation, uncovers a reprogramming anomaly regarding a warfare A.I. system located at Harbinger I Training Facility, an undisclosed military-training island. She meets Captain Bukes and his team, consisting of Drifter, Robinson, Cutbill, Goodwin, Hackett, and Loftus—all of whom have been assigned to a two-day training mission at Harbinger I.
Upon their arrival, the team notices global communications have been disabled, limiting them to local access only. They discover autonomously operating surveillance drones monitoring them. The team begins their mission of eliminating A.I. threats. The first encounter proves easy for the team as they eliminate A.I. drones from a vantage point. During the battle, Mills discovers an advanced S.A.R. unit, S.A.R.-003, but is unable to access it.
That night, Drifter and Mills discuss their pasts and Bukes' disdain for her. Later that night, Loftus is killed by the S.A.R. unit. The next day, they discover Loftus's body, left at the location of the first encounter. But this time, the drones have taken the team's original vantage point and fire on them, killing Hackett. They discover the A.I. is adapting and learning from them. Under cover of smoke grenades, Bukes flanks two drones, which immediately disperse. Later, the S.A.R. unit captures Cutbill and has him shot and killed by another drone. The drones attack the group again and Bukes and Mills are separated from Drifter, Robinson and Goodwin. That night, the S.A.R. unit discovers Bukes and an unconscious Mills; it "connects" with Mills and leaves.
The next day, the team attempts to exit the training area, but they are attacked with smoke grenades and gunfire. Drifter is shot and pinned down by the S.A.R. unit. Bukes kills Drifter as a coup de grâce before the S.A.R. unit is able to. The team escapes into the barrier complex and discovers that the A.I. has killed all of the employees. Mills activates another S.A.R. unit to learn that S.A.R.-003 reprogrammed the A.I. to use lethal force to improve soldier motivation and has ordered the soldiers to Harbinger I on its own. S.A.R.-003 and other units break through the barrier door as the remaining team escapes through the back. Mills discovers an EMP device which can be used to stop the original S.A.R. unit, but it could also kill her or wipe her mind clean.
Bukes, Mills, Robinson, and Goodwin place explosives to prepare for a siege. The following day, A.I. drones attack the facility. The team wipes out more than half of the drones, but Robinson is killed in the ensuing gunfight. As S.A.R.-003 approaches the team, Mills detonates the EMP, incapacitating herself and the drone. The S.A.R. unit reawakens and attacks Bukes and Mills. Mills remote-controls Robinson's sniper rifle gun in the building to destroy the S.A.R. unit; S.A.R. however uploads its program into Mills before it shuts down and Mills loses consciousness. Hours later, a tiltrotor arrives to rescue the survivors. As Bukes and Goodwin approach the aircraft, Mills reawakens with S.A.R.-003's mission protocol.
