Mission 1 - Osiris - Kamchatka
Fireteam Osiris is dispatched to recover the UNSC's most wanted criminal: Doctor Catherine Elizabeth Halsey.
Spoiler
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Spoiler
Locke kills Jul'Mdama. They make a character in years and kill him in seconds.
Mission 2 - Blue Team - Argent Moon
The Master Chief is reunited with his Spartan II Blue Team for a routine investigation of the lost ONI research station Argent Moon.
Mission 3 - Glassed - Meridian
Osiris must pursue Blue Team to a glassed world beyond UNSC jurisdiction.
Mission 4 - Meridian Station - Meridian
Osiris learns that Meridian Station holds many secrets.
Mission 5 - Unconfirmed - Meridian
Osiris tracks Blue Team deep below the surface of Meridian.
Mission 6 - Evacuation - Meridian
Osiris is separated from Blue Team and must race to keep up.
Mission 7 - Reunion - Genesis
Blue Team arrives at the Forerunner world Genesis where they discover the true reason for the Guardians' activation.
Mission 8 - Swords of Sanghelios - Sanghelios
When evidence reveals that the Master Chief is in danger, Fireteam Osiris' mission changes from retrieval to rescue.
Mission 9 - Alliance - Sanghelios
Osiris joins forces with the Swords of Sanghelios.
Mission 10 - Enemy Lines - Sanghelios
In order to activate a Guardian, Osiris must track down a Forerunner Constructor.
Mission 11 - Before the Storm - Sanghelios
Osiris and the Swords of Sanghelios prepare for a final battle with the Covenant.
Mission 12 - Battle of Sunaion - Sanghelios
Osiris races to reach the Guardian before it leaves Sanghelios.
Mission 13 - Genesis - Genesis
Osiris arrives on Genesis, where they meet a new ally in their battle.
Mission 14 - The Breaking - Genesis
The Master Chief and his team face their greatest threat and his hardest choice as the true power of the Guardians is revealed.
Mission 15 - The Guardians - Genesis
As Blue Team's lives hang in the balance, Osiris must save them and stop the Guardians.