In the 28th Century, the prolonged war between humanity and the fanatical alien alliance the Covenant has ended with a tenuous treaty. Despite the ceasefire, Earth's outer colonies remain vulnerable to the Covenant's covert intrusions. The ONI - Office of Naval Intelligence has been tasked with counterintelligence to beat the Covenant. In Planet Sedra, Commander Jameson Locke and his team witness a Covenant's spacecraft and a Zealot Elite warrior disembarks with a bomb. They unsuccessfully try to stop the alien that explodes the bomb in a mall. They realize that it is a biological attack with an element fatal to humans. Sedran Commander Aiken captures the middleman Axl that tells that the element is obtained from Alpha Halo, where the day longs 16 h and the temperature in the sunlight reaches 482o C. Aiken, Locke and his team head to Halo in the spacecraft Condor with pilot Macer carrying a Havoc weapon to destroy the place. On the arrival, they find two terrorists but are trapped in